Silent bird trapping bill (5)
I believe the answer is:
tacit
'silent' is the definition.
('tacit' can be a synonym of 'silent')
'bird trapping bill' is the wordplay.
'bird' becomes 'tit' (I've seen this before).
'trapping' is an insertion indicator.
'bill' becomes 'ac'.
'tit' going around 'ac' is 'TACIT'.
(Other definitions for tacit that I've seen before include "Implicitly understood" , "without speaking" , "Implied without being stated" , "Understood, not spoken or played" , "Implied or understood, not put into words" .)