Unpowered aircraft (6)
I believe the answer is:
glider
'unpowered aircraft' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for glider that I've seen before include "A sort of possum" , "Powerless aircraft" , "Plane supported by air" , "Powerless traveller" , "craft without power" .)