Neat leftist turned up in an airport (7)
I believe the answer is:
orderly
'neat' is the definition.
(I know that neat can be written as orderly)
'leftist turned up in an airport' is the wordplay.
'leftist' becomes 'red' (red can informally mean communist).
'turned up' says the letters should be written backwards.
'in' is an insertion indicator.
'an airport' becomes 'orly' (French airport).
'red' back-to-front is 'der'.
'der' placed inside 'orly' is 'ORDERLY'.
(Other definitions for orderly that I've seen before include "Well-behaved -- soldier attending to a superior officer" , "Tidy officer's attendant" , "Soldier with special duties - hospital attendant" , "Methodical, like soldier servant" , "Neatly arranged; hospital attendant" .)