Fat queen in store (6)
I believe the answer is:
larder
'store' is the definition.
(food store)
'fat queen' is the wordplay.
'fat' becomes 'lard' (lard is a kind of fat).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'lard'+'er'='LARDER'
'in' is the link.
(Other definitions for larder that I've seen before include "Place where food is kept" , "Stock of provisions" , "Pantry" , "Person applying grease" , "room off kitchen?" .)