Songbird catching a cold becomes silent (5)
I believe the answer is:
Here is my best explanation:
'silent' is the definition.
'songbird catching a cold' is the wordplay.
'songbird' becomes 'tit' (I've seen this before).
'catching' indicates putting letters inside.
'a cold' becomes 'ac' (I've seen this in other clues).
'tit' going around 'ac' is 'TACIT'.
'becomes' acts as a link.