Game won by the over-forties (6)
I believe the answer is:
tennis
'game' is the definition.
(tennis is a kind of game)
'won by the over-forties' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
The remaining letters 'ennis' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tennis that I've seen before include "Ball-game" , "Evil trap set up for game" , "Sent in (anag.)" , "Wimbledon sport" , "Sport Dwight Davis gave trophy for" .)