Slip catch turned game (6)
I believe the answer is:
Here is my best explanation:
'game' is the definition.
(tennis is a kind of game)
'slip catch turned' is the wordplay.
'slip' becomes 'sin' (I can't justify this - if you can you should believe this answer much more).
'catch' becomes 'net' (netting is a kind of catching).
'turned' shows that the letters should be reversed in order.
'sinnet' in reverse letter order is 'TENNIS'.