Neat leftie back in an airport (7)
I believe the answer is:
orderly
'neat' is the definition.
(I know that neat can be written as orderly)
'leftie back in an airport' is the wordplay.
'leftie' becomes 'red' (red can informally mean a political leftwinger).
'back' shows that the letters should be reversed in order.
'in' indicates putting letters inside.
'an airport' becomes 'orly' (French airport).
'red' in reverse letter order is 'der'.
'der' put within 'orly' is 'ORDERLY'.
(Other definitions for orderly that I've seen before include "Junior Army rank" , "Hospital attendant - neat" , "Tidy officer's attendant" , "Soldier with special duties - hospital attendant" , "Regular - neat" .)