Unmanned planes (6)
I believe the answer is:
drones
'unmanned planes' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for drones that I've seen before include "Aircraft operated by remote control" , "Honeybees that mate with the queen" , "Male bees or idlers" , "Male honey bees" , "Male honey-bee or idle people" .)