Plane control surface (7)
I believe the answer is:
aileron
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">plane control surface</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for aileron that I've seen before include "Trailing-edge flap" , "Movable wing surface" , "Movable part of an aircraft's wing" , "Hinged flap on aircraft wing" , "Wing control flap" .)