Voracious insect (6)
I believe the answer is:
locust
'voracious insect' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for locust that I've seen before include "Sort of migratory grasshopper" , "Destructive winged insect" , "Migratory crop stripper" , "Predatory grasshopper that swarms" , "Part of destructive plague" .)