Knaves with King in poker, maybe (5)
I believe the answer is:
cards
'poker maybe' is the definition.
(I know that poker is a cards)
'knaves with king' is the wordplay.
'knaves' becomes 'cads' (I've seen this in another clue).
'with' indicates putting letters inside.
'king' becomes 'R' (abbreviation of Latin rex).
'cads' going around 'r' is 'CARDS'.
'in' is the link.
(Other definitions for cards that I've seen before include "Get one's -----: it's a P45 nowadays!" , "Small pieces of stiff paper" , "Christmas post" , "Odd people" , "They may be for playing or greeting" .)