What will Jack do? That bloke's going to cause trouble! (5,4)
I believe the answer is:
raise hell
'cause trouble' is the definition.
(to raise hell is to cause trouble or commotion)
'what will jack do? that bloke's going to' is the wordplay.
'what will jack do?' becomes 'raise' (a jack raises something up).
'that bloke' becomes 'he' ('he' refers to a man).
'going to' becomes 'll' (as in he'll, we'll etc).
'raise'+'he'+'ll'='RAISE HELL'
(Other definitions for raise hell that I've seen before include "create discord" , "create commotion" , "complain vociferously" , "Complain in the strongest possible terms" , "Make trouble" .)