Musical work starting off piano, ultimately strident (4)
I believe the answer is:
opus
'musical work' is the definition.
(I've seen this before)
'starting off piano ultimately strident' is the wordplay.
'starting' suggests taking the first letters.
The first letters of 'off piano ultimately strident' is 'OPUS'.
(Other definitions for opus that I've seen before include "Showing creative skill" , "Piece of music (with number)" , "Musical piece" , "Work (of a composer?)" , "Composition - magnum __" .)