Bird flying (5)
I believe the answer is:
swift
This clue is a double definition.
'bird' is the first definition.
(swift is a kind of bird)
'flying' is the second definition.
(thesaurus)
(Other definitions for swift that I've seen before include "Fast-moving bird" , "writer of satire" , "Racy" , "Fast - novelist" , "Happening quickly; author" .)