Dig for food (4)
I believe the answer is:
grub
This clue is a double definition.
'dig' is the first definition.
(thesaurus)
'food' is the second definition.
(grub is a kind of food)
'for' is the link.
(Other definitions for grub that I've seen before include "food, commonly" , "Insect larva or slang food (4)" , "Slang food for worm-like larva" , "Larva; food (sl.)" , "Worm-like larva of an insect" .)