Plane- wing part (7)
I believe the answer is:
aileron
'plane-wing part' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aileron that I've seen before include "Movable part of an aircraft's wing" , "Aeroplane's wing flap" , "seen on the wing" , "Hinged flap an an aeroplane wing" , "Trailing-edge flap" .)