Insect larva as food (4)
I believe the answer is:
grub
I believe this clue is a double definition.
'insect larva' is the first definition.
(grub is a type of insect larva)
'food' is the second definition.
(grub can informally mean food)
'as' acts as a link.
(Other definitions for grub that I've seen before include "ferret > eats" , "Insect larva or slang food (4)" , "Slangy food or kind of larva" , "Larva; food (sl.)" , "Beetle larva" .)