Flyer's collapse, having swallowed insect (7)
I believe the answer is:
fantail
'flyer's' is the definition.
(type of bird)
'collapse having swallowed insect' is the wordplay.
'collapse' becomes 'fail' (I've seen this before).
'having swallowed' means one lot of letters goes inside another.
'insect' becomes 'ant' (ant is a kind of insect).
'fail' placed around 'ant' is 'FANTAIL'.
(Other definitions for fantail that I've seen before include "In a flat (anag.)" , "Flier" , "Bird" , "Type of domestic pigeon" , "Variety of pigeon" .)