Swarming grasshopper (6)
I believe the answer is:
locust
'swarming grasshopper' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for locust that I've seen before include "plaguey type" , "Clouts (anag)" , "Vegetation-destroying grasshopper" , "Migratory crop stripper" , "It strips plants" .)