Topless witches' appliance (4)
I believe the answer is:
oven
'appliance' is the definition.
(oven is a kind of appliance)
'topless witches'' is the wordplay.
'topless' means to remove the first letter.
'witches'' becomes 'coven' (a coven is a group of witches).
'coven' with its first letter taken away is 'OVEN'.
(Other definitions for oven that I've seen before include "You can cook in this" , "Enclosed chamber for cooking" , "Kiln, cooker" , "Hot spot" , "Cooker; furnace" .)