Hot coal (5)
I believe the answer is:
ember
'hot coal' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ember that I've seen before include "Piece of live coal" , "Glowing remainder of a fire" , "something that glows" , "what causes a warm glow" , "Glowing coal; prayer (Days)" .)