Nourishment in fruit eaten by insect (7)
I believe the answer is:
aliment
'nourishment' is the definition.
(synonyms)
'fruit eaten by insect' is the wordplay.
'fruit' becomes 'lime' (lime is a kind of fruit).
'eaten by' is an insertion indicator (inserted letters get eaten).
'insect' becomes 'ant' (ant is a kind of insect).
'lime' inserted within 'ant' is 'ALIMENT'.
'in' acts as a link.
(Other definitions for aliment that I've seen before include "Old word for food" , "Nourishment" , "Something which nourishes - meal tin (anag)" , "Sustenance" .)