Sound from piano is excruciating (5)
I believe the answer is:
noise
'sound' is the definition.
(a noise is a sound)
'from piano is excruciating' is the wordplay.
'from' says the answer is hidden in the clue.
'NOISE' is hidden in the letters of 'piano is excruciating'.
(Other definitions for noise that I've seen before include "Confused sounds" , "Commotion" , "Unwelcome sound" , "Static - sound" , "Loud or disturbing sound" .)