Parlay has a king thus functioning (2,4)
I believe the answer is:
in play
'functioning' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for in play that I've seen before include "(Of ball) able to be used in game" , "performing publicly?" , "on the field" , "not out of bounds" , "dead? On the contrary" .)