Marked card (6)
I believe the answer is:
ticket
'card' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for ticket that I've seen before include "Coupon, admission voucher" , "Token for admission" , "Parking offence notice" , "Maybe single" , "Entry/travel permit" .)