Fat monarch makes room for food (6)
I believe the answer is:
larder
'room for food' is the definition.
(room where food is kept)
'fat monarch' is the wordplay.
'fat' becomes 'lard' (lard is a kind of fat).
'monarch' becomes 'ER' (abbreviation for Elizabeth Regina, British Queen).
'lard'+'er'='LARDER'
'makes' is the link.
(Other definitions for larder that I've seen before include "Place where food is kept" , "Food store" , "Room or cupboard for food storage" , "Cool store" , "room off kitchen?" .)