Card game for one player (9)
I believe the answer is:
solitaire
'card game for one player' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for solitaire that I've seen before include "Patience game" , "songbird" , "Single stone in jewellery" , "Patience of Americans" , "One-gem ring; one-player game" .)