Suspend professional prankster (8)
I believe the answer is:
prorogue
'suspend' is the definition.
(thesaurus)
'professional prankster' is the wordplay.
'professional' becomes 'pro' ('pro' can be a synonym of 'professional').
'prankster' becomes 'rogue' (I've seen this before).
'pro'+'rogue'='PROROGUE'
(Other definitions for prorogue that I've seen before include "Discontinue meeting" , "Discontinue (a session of parliament)" , "Suspend meeting" , "Suspend, postpone" , "Stop meeting" .)