Butterfly or moth larva (11)
I believe the answer is:
caterpillar
'butterfly or moth larva' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for caterpillar that I've seen before include "crawler" , "looper, perhaps" , "Heavy tracked earth-moving vehicle" , "Moth/ butterfly larva" , "future monarch, perhaps" .)