Joker or Jack? (4)
I believe the answer is:
card
I believe this clue is a double definition.
'joker' is the first definition.
(joker is a type of playing card)
'jack?' is the second definition.
(jack is a kind of card)
'or' acts as a link.
(Other definitions for card that I've seen before include "Comb (wool)" , "A jack, for example" , "Thick paper" , "amusing character" , "Heart or club, say?" .)