Black jack, half the time (4)
I believe the answer is:
club
'black jack half the time' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for club that I've seen before include "Place to meet one's friends with a weapon" , "Staff - association" , "Golf requisite" , "women expect to be in" , "woman expects to be in" .)