A win for the second time (5)
I believe the answer is:
again
'the second time' is the definition.
(I've seen this before)
'a win' is the wordplay.
'win' becomes 'gain' (synonyms).
'a'+'gain'='AGAIN'
'for' acts as a link.
(Other definitions for again that I've seen before include "'Another time, once more (5)'" , "Here we go ___" , "Next time" , "On the other hand" , "Ocne more" .)