Roasting inside oven (4)
I believe the answer is:
oast
'oven' is the definition.
(oast is a kind of oven)
'roasting inside' is the wordplay.
'inside' indicates a hidden word.
'OAST' can be found hidden inside 'roasting'.
(Other definitions for oast that I've seen before include "Hop-drier" , "Hop drying kiln" , "Kiln for drying hops or malt" , "Oven for hops" , "Where to cook" .)