Oven used in roasting (4)
I believe the answer is:
oast
'oven' is the definition.
(type of kiln)
'in roasting' is the wordplay.
'in' indicates a hidden word.
'OAST' is hidden within 'roasting'.
'used' is the link.
(Other definitions for oast that I've seen before include "Hop drying kiln" , "Hop-drying kiln" , "Kiln for drying hops or malt" , "Hop-drier" , "Oven for hops" .)