Revellers’ options just before November (5,2,5)
I believe the answer is:
trick or treat
'november' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I don't understand the rest of the clue.
(Other definitions for trick or treat that I've seen before include "Children's protection racket at Hallowe'en?" , "October 31 blackmail" , "Halloween ordeal?" , "Halloween custom" , "Unwelcome Halloween tradition" .)