Banking controller? (7)
I believe the answer is:
aileron
'banking controller?' is the definition.
(part of a plane controlling its tilting or banking)
This is the entire clue.
(Other definitions for aileron that I've seen before include "Banking controller" , "An oriel, strangely, on an aircraft" , "Wing control flap" , "One helps to control banking" , "Movable part of an aircraft's wing" .)