The second stanza reads:
So sung a little Clod of ClayTrodden with the cattle's feet,But a Pebble of the brookWarbled out these metres meet
A 'strong' image in this instance would be 'Clod of Clay'. Literally, a clod would be a lump, chunk or piece of something. Clay, by definition, is grained earth or sand which is heavy and sticky when wet. When it is wet
it is malleable and can be shaped. In this regard it is used to create pottery, artistic pieces (such as statues) and bricks. The lump of clay in this context is small.
In a figurative sense, the word, 'little' suggests something insignificant or hardly noteworthy and insinuates that the opinion or perspective of the clod of clay is of very little importance - its version of things, however, has to be considered.
The clay is obviously personified and the poem suggests that
because the clay is malleable and easily formed and 'little', it is young and inexperienced and has not yet been hardened by experience. This means that its view of love is naïve and uninformed. It presents a very idealistic and romantic notion of love. In its innocence it is of the opinion that love is unselfish and could bear whatever abuse and challenges it could encounter.
Another view could be that the clay is being stupid to believe that its version of love is true. The word 'clod' in this instance could be interpreted as meaning unintelligent. The implication is that the clay lacks the foresight or intellectual capacity to fully understand the concept of love.