In 'Piano' by D.H. Lawrence, what aspects of the poem relate to childhood?
So, I'm guessing that by "aspect", you mean the theme of childhood. I've pulled some quotations that we can analyze for that theme.
"Taking me back down the vista of years, till I see / A child sitting under the piano [...] / And pressing the small, poised feet of a mother who smiles as she sings"
Lawrence is listening to a woman sing, and he is reminded of a scene. In this scene, another woman is singing, but this time to a child. Because he notes that he has been taken down "the vista of years", it is apparent that this is one of his own memories. The reader can assume from the tone of nostalgia that he is the child.
"the heart of me weeps to belong / to the old Sunday evenings at home"
Here, the key word is "old", which indicates that these days, like Lawrence's childhood, are now passed.
"The glamour / Of childish days is upon me"
Adults tend to feel nostalgia about their childhoods, and many people tend to remember them fondly to the point of forgetting the pain or negative aspects of childhood. As a result, he says that this "glamour" is now "upon" him, or taken control of him.
"my manhood is cast / Down in a flood of remembrance, I weep like a child for the past"
By remembering his childhood so sadly and with such desire, Lawrence is actually transformed back into a child, crying for the things he cannot have.