Fat English king’s food store (6)
I believe the answer is:
larder
'food store' is the definition.
(I've seen this before)
'fat english king's' is the wordplay.
'fat' becomes 'lard' (lard is a kind of fat).
'english' becomes 'e' (abbreviation).
'king' becomes 'R' (abbreviation for rex, king in Latin).
'lard'+'e'+'r'='LARDER'
(Other definitions for larder that I've seen before include "Cupboard or small room for food" , "Person applying grease" , "room off kitchen?" , "Room or cupboard for food storage" , "Place where food is kept" .)