French leader measures birds (7)
I believe the answer is:
'birds' is the definition.
(finch is a kind of bird)
'french leader measures' is the wordplay.
I cannot quite see how this works, but
'french' could be 'f' (abbreviation) and 'f' is located in the answer.
'leader' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
'measures' could be 'hs' (H is an example) and 'hs' is located in the remaining letters.
The remaining letters 'inc' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for finches that I've seen is " Numerous small songbirds".)