Insect kept in ferret's food store (6)
I believe the answer is:
pantry
'food store' is the definition.
(cupboard for storing food)
'insect kept in ferret's' is the wordplay.
'insect' becomes 'ant' (ant is a kind of insect).
'kept in' means one lot of letters goes inside another.
'ferret' becomes 'pry' (both can mean to seek information).
'ant' placed within 'pry' is 'PANTRY'.
(Other definitions for pantry that I've seen before include "Small storeroom for food etc" , "Store cupboard" , "Type of larder" , "Small room or cupboard for storing food" , "Room off the kitchen" .)