Oven; oast (4)
I believe the answer is:
kiln
I believe this clue is a double definition.
'oven' is the first definition.
(kiln is a kind of oven)
'oast' is the second definition.
(I've seen this in another clue)
(Other definitions for kiln that I've seen before include "Oven for burning lime" , "Drying furnace" , "Hops or pottery cooker?" , "Baker" , "Oven for hardening and drying" .)