UFO pilots (3)
(Another definition for ets that I've seen is " Who teach soldiers".)
'ufo pilots' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aliens that I've seen before include "Immigrants" , "Outer space creatures, perhaps from Mars?" , "'Little green men'?" , "Creatures from another planet" , "Foreigners or extraterrestrials" .)