Oven-safe glassware (5)
I believe the answer is:
pyrex
'oven-safe glassware' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pyrex that I've seen before include "Heat-proof ovenware" , "Heatproof glass" , "Heat-resistant glassware used in cooking" , "Heat-resistant glass" .)