Plane without an engine (6)
I believe the answer is:
glider
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">plane without an engine</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 glider that I've seen before include "Powerless traveller" , "Engineless plane" , "Girdle for silent flier" , "Plane supported by air" , "craft without power" .)