It's often preheated (4)
I believe the answer is:
oven
'it's often preheated' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for oven that I've seen before include "Stove" , "Metal box in which to roast" , "Place for burning" , "It may get very hot" , "Kiln, cooker" .)