Pieces of rat's tail quietly consumed by someone struggling (4,5)

'pieces' is the definition.
(tone poem is a kind of piece)

'rat's tail quietly consumed by someone struggling' is the wordplay.
I cannot really understand how this works, but
'quietly' could be 'p' (p for piano and quiet) and 'p' is found in the answer.
an anagram of 'someone' is 'oneoems' which is within the remaining letters.
A single letter 't' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

'of' acts as a link.

Can you help me to learn more?