Pound with sound (6)
I believe the answer is:
deafen
'pound with sound' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for deafen that I've seen before include "Render senseless" , "Make unable to hear" , "Burst the eardrums" , "have a stunning effect" , "Drown out" .)