Air force heroes (4)
I believe the answer is:
aces
'air force heroes' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aces that I've seen before include "Two will make deuce" , "They're high and low on cards" , "Tennis serves the receiver can't reach" , "Ones or elevens in cards" , "Experts (in their field)" .)