Christmas in no time, school ends (4)
I believe the answer is:
noel
'christmas' is the definition.
(synonyms)
'no time school ends' is the wordplay.
'ends' says to take the final letters.
The final letters of 'time school' are 'el'.
'no'+'el'='NOEL'
'in' is the link.
(Other definitions for noel that I've seen before include "Christmas carol" , "Coward who wrote and acted, d. 1973" , "A lone French Christmas" , "Festive season" , "Yuletide" .)