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