Food in immature form (4)

I believe the answer is:

grub

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'food' is the definition.
(grub can informally mean food)

I can't explain the remainder of the clue.

(Other definitions for grub that I've seen before include "Larva; dig shallowly" , "Dig - maggot - food" , "Table needs" , "ferret > eats" , "Common food" .)

I've seen this clue in the Evening Standard.

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