Winnings thanks to court cards (7)
I believe the answer is:
takings
'winnings' is the definition.
(takings can mean winnings or profits)
'thanks to court cards' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'to court cards' becomes 'kings' (king is a kind of court card).
'ta'+'kings'='TAKINGS'
(Other definitions for takings that I've seen before include "Income from transactions" , "Cash receipts" , "Income from sales, etc" , "gold received?" , "Monetary receipts" .)