Perhaps match was unfinished. Not odd! (4)
I believe the answer is:
even
'not odd' is the definition.
('even' is the opposite to 'odd')
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for even that I've seen before include "notwithstanding" , "time of day" , "Constant" , "Equally balanced; level" , "Deep crisp snow seen on Boxing Day also this" .)