Christmas drink (6)
I believe the answer is:
eggnog
'christmas drink' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for eggnog that I've seen before include "Yellowish mixed alcoholic drink" , "Festive dairy beverage" , "Drink (milk punch)" , "Hot alcoholic drink" , "Fortified drink similar to a flip" .)