Move silently, forbidden to speak, beating team (5,4)
I believe the answer is:
steel band
'beating team' is the definition.
'move silently forbidden to speak' is the wordplay.
'move silently' becomes 'steel' (I can't explain this - if you can you should give a lot more credence to this answer).
'forbidden' becomes 'banned' (banning is a kind of forbidding).
'to speak' indicates a 'sounds like' (homophone) clue.
'banned' is a homophone of 'band'.
'steel'+'band'='STEEL BAND'
(Other definitions for steel band that I've seen before include "drummers" , "Musicians playing oil drums" , "Caribbean musicians" , "Team of beaters" , "Caribbean ensemble" .)