The musicians are proscribed, we hear (4)
I believe the answer is:
band
'the musicians' is the definition.
(group of musicians)
'proscribed we hear' is the wordplay.
'proscribed' becomes 'banned' (banning is a kind of proscribing).
'we hear' shows a homophone (sound like).
'banned' is a homophone of 'BAND'.
'are' is the link.
(Other definitions for band that I've seen before include "Musicians - gang" , "Orchestra" , "Belt; group of musicians" , "Players" , "Strip, belt; playing group" .)