Form of criminal's bird done before time ends (10)
I believe the answer is:
constitute
'form' is the definition.
('constitute' can be a synonym of 'form')
'criminal's bird done before time ends' is the wordplay.
I cannot quite understand how this works, but
'criminal's' could be 'cons' (abbreviation for 'convict') and 'cons' is found within the answer.
'bird' could be 'tit' (I've seen this before) and 'tit' is present in the answer.
'done' could be 'u' and 'u' is found in the answer.
'time' could be 't' and 't' is found in the answer.
A single letter 'e' remains which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for constitute that I've seen before include "Found" , "form" , "Make up" , "Be (a part) of a whole" .)