I agree with the other educators that the quote is difficult to fully absorb apart from the whole of the passage. This passage comes from the poem “Twins” by E. B. White, the same author who penned Charlotte’s Web and Stuart Little. It can be found in the collection Poems and Sketches of E. B. White.

There is a profound parallel in this particular passage between the sun struggling to shine and the images evoked by the fawns. Fawns, at least when first born, are gangly, spindly-legged creatures that tend to explore their surroundings tentatively. They appear fragile and yet represent the hope and endless possibilities of life itself. The same can be said of the sun. The sun can appear weak (fragile), but even on the cloudiest of days we all know that the sun is endlessly working to break through and that the clouds can never hold it back for long.

One other thing to consider—fawns in nature are very rarely seen except at dawn or dusk. You’ll notice that the passage doesn’t actually say that the sun is breaking through clouds. Because the sun and the fawns are brought together so neatly in the image White creates, I would say that the sun is breaking through the horizon, not just clouds. That places the timing of the image at sunrise, yet another symbol of newness and possibilities.

So, how does the word “kindled” work for this passage? Again, to “kindle” a fire is to begin something new, something that will hopefully take on a life of its own. It is the perfect word to meld together the brightness of the sun with the fragile beauty of the fawns. It gives the image light, but a gentle light, one that grows incrementally brighter as the fawns grow incrementally more confident in their surroundings.

If White had chosen “the sun burst through,” it would have completely altered the tone and imagery of the passage. Gone would be that hint of fragility, of gentleness, and untapped potential. The sun would no longer share those commonalities with the fawns, and the entire passage would fall apart. It would cease to be an evocative image of new life and become an everyday Twitter post. It would cease to be poetry and become something . . . less.

A fire that is "kindled" is not one that bursts roaring into life. Kindling suggests an element of coaxing, a fire that begins as a gently smoldering flame which grows through dedicated effort. In this sentence, the act of the white spots being kindled indicates a gentle and gradual warming of the spots, as if lit from within by a slow burning flame.

In keeping with this, for the sun to break through suggests that the process is both effortful and gradual. Were the sun to burst through, it would likely set the white spots ablaze, but a breaking sun emerges piece by piece and coaxes light to kindle. This verb far better suits the sentence, although objectively the word "burst" obviously suggests stronger and more active motion.

A sun "bursting" would seem to put an end to any kindling—it would imply the gradual illumination was over, to be replaced by a flood of light.

Without knowing the original passage and the larger work, it can be difficult to parse the meaning of a sentence like the one in question. However, we can make a few guesses by looking closely at the words and their definitions and relationship to each other.

To "kindle" means to start burning, or to stir up. So the flame in question is "stirring up" the white spots on the fawns, as if causing those white spots to catch on fire. "Kindling a fire" means starting a small fire by rubbing sticks together or using a small flame (like a lighter) to ignite the "kindling," which are small branches. Eventually, the small flames you've kindled grow into a larger fire.

Again, it's difficult to guess the purpose of this sentence without knowing what information comes before and after. However, the language does personify the sun as weak, and the fact that the sun breaks weakly through the clouds emphasizes that the sun is struggling to shine on the young deer below, to bring out their fire-like beauty.

Furthermore, the sun's weakness parallel's the fact that the fawns are young and, we can assume, relatively weak. So changing "broke weakly" to "burst" would destroy that similarity, and give the sentence a much more triumphant tone, rather than the tone of understated struggle that's currently present. Again, whether that change would strengthen or weaken the sentence depends on the context (what comes before and after).

Finally, if "broke weakly" were changed to "burst", the sun's flame would clearly be a very big, powerful flame, rather than the weak but fighting flame that is currently implied. Such a change would alter the dynamics of the images here, and alter the tone, though for better or worse is for you to decide. Consider which of the two versions is more fitting for the larger piece in question--which is more in keeping with the emotions, themes, and imagery of the rest of the paragraph, and of the work as a whole?