Yell not acceptable after request for silence (5)
I believe the answer is:
shout
'yell' is the definition.
(I know that yell can be written as shout)
'not acceptable after request for silence' is the wordplay.
'not acceptable' becomes 'out' (cricket term).
'after' is a charade indicator (letters next to each other).
'request for silence' becomes 'sh' ('sh' is used to tell someone to be quiet).
'out' after 'sh' is 'SHOUT'.
(Other definitions for shout that I've seen before include "Loud call" , "bellow" , "Yell" , "Call loudly" , "Raise one's voice" .)