Happy union's no-score draw? (4,5)
I believe the answer is:
Here is my best explanation:
'happy union's' is the definition.
'no-score draw?' is the wordplay.
'no score' becomes 'love' (I've seen this before).
'draw?' becomes 'match' (draw is a type of match).
(Other definitions for love match that I've seen before include "Basis of successful partnership", "Marriage based on real affection", "No score draw", "This is not just a convenient arrangement", "comes to nothing for one party [IN?] court?", "Not an arranged marriage", "There's nothing to equal", "romantic marriage", "Sort of marriage" and "passionate union meeting".)