Airily departing singer? (4)
I believe the answer is:
swan
'singer?' is the definition.
(swan is a kind of birdanimal)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for swan that I've seen before include "Whooper, perhaps" , "Kind of song, in the end" , "Shakespeare is called The .... of Avon" , "Cob - pen" , "Long-necked water bird" .)