Food in unlimited piles (4)
I believe the answer is:
tack
'food' is the definition.
(I've seen this in other clues)
'unlimited piles' is the wordplay.
'unlimited' indicates the central letters (discard the edges or 'limits' of the word).
'piles' becomes 'stacks' (pile can mean a stack of something).
The central letters of 'stacks' are 'TACK'.
'in' acts as a link.
(Other definitions for tack that I've seen before include "Cheap material; nail" , "Food; nail" , "Small nail with broad head" , "policy" , "Nail; course of action" .)