Oats cooked in oven (4)
I believe the answer is:
oast
'oven' is the definition.
(oast is a kind of oven)
'oats cooked' is the wordplay.
'cooked' indicates an anagram.
'oats' is an anagram of 'OAST'.
'in' is the link.
(Other definitions for oast that I've seen before include "Hop drying kiln" , "Where to cook" , "Drying house" , "Hop-drier" , "Oven for hops" .)