... on the other hand, the knight gets a win (4,5)
I believe the answer is:
then again
'on the other hand' is the definition.
('then again' can be a synonym of 'on the other hand')
'the knight gets a win' is the wordplay.
'knight' becomes 'n' (chess).
'gets' is a charade indicator (letters next to each other).
'win' becomes 'gain' ('gain' can be a synonym of 'win'**).
'the'+'n'+'a'+'gain'='THEN AGAIN'
(Other definitions for then again that I've seen before include "still" , "however" , "From another point of view" .)