Card to beat (4)
I believe the answer is:
club
I believe this clue is a double definition.
'card' is the first definition.
(club is a kind of card)
'beat' is the second definition.
(I've seen this before)
'to' acts as a link.
(Other definitions for club that I've seen before include "Kind of weapon or golf stick" , "Place to meet one's friends with a weapon" , "Truncheon" , "member in black suit > bash" , "See 1" .)