Christmas prize giver, heartless (4)
I believe the answer is:
noel
'christmas' is the definition.
('Noel' can be a synonym of 'christmas')
'prize giver heartless' is the wordplay.
'prize giver' becomes 'nobel' (I've seen this before).
'heartless' means to remove the middle letters.
'nobel' with its centre taken out is 'NOEL'.
(Other definitions for noel that I've seen before include "Christmas, in cards" , "Religious festival" , "present time" , "A lone French Christmas" , "Christmas carol" .)