Service some aircraft (3)
I believe the answer is:
raf
'service' is the definition.
'some aircraft' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'RAF' can be found hidden inside 'aircraft'.
(Other definitions for raf that I've seen before include "Royal Air Force (abbr.)" , "It fought Battle of Britain" , "Airforce of Great Britain" .)