March saint is surprisingly celebrated in December (9)
I believe the answer is:
christmas
'in december' is the definition.
(I know that Christmas is part of Dec)
'march saint is surprisingly celebrated' is the wordplay.
I cannot really see how this works, but
'saint' could be 'st' (abbreviation) and 'st' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for christmas that I've seen before include "Yule, Noel" , "SECOND PART OF 1 ACROSS" , "Holy festival" , "see 11" , "Winter festival" .)