Bung joint in bloke's case (5)
I believe the answer is:
bribe
'bung' is the definition.
(bung can mean a bribe)
'joint in bloke's case' is the wordplay.
'joint' becomes 'rib' (ribs are joints).
'in' indicates putting letters inside.
'case' means to remove the middle letters.
'bloke' with its middle taken out is 'be'.
'rib' inserted within 'be' is 'BRIBE'.
(Other definitions for bribe that I've seen before include "Illegal incentive" , "Illegal inducement" , "Kickback" , "Sweetener, back-hander" , "Dishonestly persuade" .)