Lacking a game to play - or rivals (9)
I believe the answer is:
matchless
'lacking a' is the definition.
I can't judge whether this defines the answer.
'game to play or rivals' is the wordplay.
I cannot quite see how this works, but
'game' could be 'match' (eg a football match) and 'match' is present in the answer.
The remaining letters 'less' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for matchless that I've seen before include "Unrivalled" , "reason for rubbing sticks together?" , "Unparalleled" , "Like the top" , "Perfect" .)