Bird holding account becomes silent (5)
I believe the answer is:
tacit
'silent' is the definition.
(I know that silent can be written as tacit)
'bird holding account' is the wordplay.
'bird' becomes 'tit' (tit is a kind of bird).
'holding' is an insertion indicator.
'account' becomes 'ac' (abbreviation for account).
'tit' enclosing 'ac' is 'TACIT'.
'becomes' is the link.
(Other definitions for tacit that I've seen before include "Understood, implicit" , "Implied, unstated" , "Implicitly understood" , "Wordless" , "Understood, not spoken or played" .)