Donkey in the Christmas story (3)
I believe the answer is:
ass
'donkey' is the definition.
(ass is a term for a donkey)
'in the christmas story' is the wordplay.
'in' says the answer is hidden in the clue.
'ASS' is hidden within 'christmas story'.
(Other definitions for ass that I've seen before include "Titania loved one" , "Stupid fellow" , "Horse relative" , "Trump's behind" , "Donkey or silly person" .)