Playing cards with rulers (5)
I believe the answer is:
kings
This clue is a double definition.
'playing cards' is the first definition.
(king is a kind of playing card)
'rulers' is the second definition.
(king is a kind of ruler)
'with' acts as a link.
(Other definitions for kings that I've seen before include "two books in > a number of colleges" , "Two book of the Old Testament" , "Men promoted" , "Rulers" , "Name of two Old Testament books" .)