He painted a flier circling the air terminal (5)
I believe the answer is:
corot
'he painted' is the definition.
(I've seen this before)
'a flier circling the air terminal' is the wordplay.
'a flier' becomes 'coot' (coot is a kind of birdanimal).
'circling' means one lot of letters goes inside another (circling can mean going around or containing).
'the air terminal' becomes 'r' (I am not sure about this - if you are sure you should believe this answer much more).
'coot' going around 'r' is 'COROT'.
Can you help me to learn more?
(Other definitions for corot that I've seen before include "C19 French landscape painter" , "Barbizon School artist" , "French artist" , "19th century French painter" , "French landscape painter, d. 1875" .)