Vehicle with a turret (4)
I believe the answer is:
tank
'vehicle with a turret' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tank that I've seen before include "Large storage chamber" , "Armoured vehicle; large container" , "Combat vehicle" , "Possible alternative to barrel" , "Aquarium; army vehicle" .)