Men wittier when drunk -- that includes Noel (10)
I believe the answer is:
wintertime
'that includes noel' is the definition.
(Christmas or Noel takes place in winter)
'men wittier when drunk' is the wordplay.
'when drunk' indicates anagramming the letters (I've seen this in other clues).
'men'+'wittier'='menwittier'
'menwittier' anagrammed gives 'WINTERTIME'.
(Other definitions for wintertime that I've seen before include "Season" , "when cold" .)