Airman adjusting a rifle (5)
I believe the answer is:
flier
'airman' is the definition.
(synonyms)
'adjusting a rifle' is the wordplay.
'adjusting' is an anagram indicator.
'rifle' is an anagram of 'FLIER'.
(Other definitions for flier that I've seen before include "Good start" , "PO, for example" , "Turkey perhaps?" , "Risk" , "Advertising leaflet" .)