Airman in a hole having only half a loaf (5)
I believe the answer is:
pilot
'airman' is the definition.
(I know that pilot is a type of aircraft pilot)
'hole having only half a loaf' is the wordplay.
'hole' becomes 'pit' (a pit is a large hole).
'having' is an insertion indicator.
'only half' means to take half the letters.
'loaf' cut in half is 'lo'.
'pit' placed around 'lo' is 'PILOT'.
'in a' is the link.
(Other definitions for pilot that I've seen before include "One-off programme" , "Steer, test (scheme)" , "-- Whale; -- light" , "Experimental scheme; flyer" , "Ship's guide" .)