Against getting into Yuletide romance? (5)
I believe the answer is:
novel
'romance?' is the definition.
(romance is a kind of novel)
'against getting into yuletide' is the wordplay.
'against' becomes 'v' (abbreviation for 'versus').
'getting into' means one lot of letters goes inside another.
'yuletide' becomes 'noel' ('Noel' can be a synonym of 'yuletide').
'v' inserted into 'noel' is 'NOVEL'.
(Other definitions for novel that I've seen before include "Fictional work" , "She, for example" , "Interestingly new; book" , "Volume of prose fiction" , "Previously unknown" .)