Rock group excluded when heard (4)
I believe the answer is:
band
'rock group' is the definition.
(I've seen this in another clue)
'excluded when heard' is the wordplay.
'excluded' becomes 'banned' (ban can mean to exclude).
'when heard' indicates a 'sounds like' (homophone) clue.
'banned' sounds like 'BAND'.
(Other definitions for band that I've seen before include "Outline drawing" , "Ring or musical group (4)" , "Strip, belt; playing group" , "Belt; group of musicians" , "Music ensemble" .)