Very hot cooker element includes oven (8)
I believe the answer is:
roasting
'very hot' is the definition.
(I've seen this before)
'cooker element includes oven' is the wordplay.
'cooker element' becomes 'ring' (eg a gas ring).
'includes' is an insertion indicator.
'oven' becomes 'oast' (type of kiln).
'ring' enclosing 'oast' is 'ROASTING'.
(Other definitions for roasting that I've seen before include "Lots of criticism" , "Very hot" , "lecture" , "Organist (anag)" , "Cooking; severe criticism" .)