Airmen coming north a long way (3)
I believe the answer is:
far
'a long way' is the definition.
(I've seen this before)
'airmen coming north' is the wordplay.
'airmen' becomes 'raf'.
'coming north' is a reversal indicator.
'raf' in reverse letter order is 'FAR'.
(Other definitions for far that I've seen before include "A long, long way to go" , "Very much" , "Distant" , "Remote" , "At a great distance way" .)