Picnic raiders (4)
I believe the answer is:
ants
'picnic raiders' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ants that I've seen before include "Six-foot insects" , "Termites" , "They live in a formicary" , "24 [INSECT] s" , "Hard workers" .)