Stick-up in Istanbul casbah (4)
I believe the answer is:
club
'stick' is the definition.
(club is a kind of stick)
'up in istanbul casbah' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'in' says the answer is hidden in the clue.
'bulc' can be found hidden inside 'istanbul casbah'.
'bulc' written backwards gives 'CLUB'.
(Other definitions for club that I've seen before include "Driver possibly" , "Golf requisite" , "Place for dance" , "member in black suit > bash" , "See 1" .)