Satisfactory in a card game (5)
I believe the answer is:
poker
'card game' is the definition.
(I know that poker is a type of card game)
'satisfactory in a' is the wordplay.
'satisfactory' becomes 'ok' (similar in meaning).
'in' is an insertion indicator.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'ok' placed within 'per' is 'POKER'.
(Other definitions for poker that I've seen before include "Fire-raiser" , "Fireside implement - card game" , "Ashes stirred by this" , "Park/zoo attendant" , "One of many irons in the fire" .)