A brilliant game (9)
I believe the answer is:
solitaire
'game' is the definition.
(I know that Solitaire is a patience)
'a brilliant' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
'brilliant' could be 'lit' (brilliant can mean shining or lit up) and 'lit' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for solitaire that I've seen before include "Card game for one player" , "[PATIENCE], especially in America" , "thrush" , "Patience of Americans" , "Patience game" .)