Positive aspect of winning team (6)
I believe the answer is:
upside
'positive aspect' is the definition.
(I've seen this before)
'winning team' is the wordplay.
'winning' becomes 'up' (I've seen this in other clues).
'team' becomes 'side' (I've seen this before).
'up'+'side'='UPSIDE'
'of' acts as a link.
(Other definitions for upside that I've seen before include "Positive aspect of a situation" , "Favourable aspect" , "advantage" , "Top surface of something" .)