Wallop opening oven (7)
I believe the answer is:
tandoor
'oven' is the definition.
(type of Asian oven)
'wallop opening' is the wordplay.
'wallop' becomes 'tan' (I've seen this in another clue).
'opening' becomes 'door' (I've seen this in another clue).
'tan'+'door'='TANDOOR'
(Other definitions for tandoor that I've seen before include "It has food cooked" , "Clay oven" , "Indian oven" .)