Nocturnal hunters (4)
I believe the answer is:
owls
'nocturnal hunters' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for owls that I've seen before include "Nocturnal bird" , "Avian symbols of wisdom" , "Strigiform creatures" , "Slow kind of birds" , "Slow sort of birds" .)