About right day for Joker? (4)
I believe the answer is:
card
'joker?' is the definition.
(joker is a type of playing card)
'about right day' is the wordplay.
'about' becomes 'ca' (circa).
'right' becomes 'r' (abbreviation).
'day' becomes 'd' (abbreviation for day).
'ca'+'r'+'d'='CARD'
'for' is the link.
(Other definitions for card that I've seen before include "Heart or club, say?" , "Piece of stiff paper" , "Bit of a wag - joker, perhaps" , "What may be used for greeting" , "amusing character" .)