Postpone in favour of a scoundrel (8)
I believe the answer is:
prorogue
'postpone' is the definition.
(thesaurus)
'in favour of a scoundrel' is the wordplay.
'in favour of' becomes 'pro' (being pro a particular cause).
'a scoundrel' becomes 'rogue' (rogue is a kind of scoundrel).
'pro'+'rogue'='PROROGUE'
(Other definitions for prorogue that I've seen before include "Discontinue meeting" , "Suspend meeting" , "Stop meeting" , "Suspend, postpone" , "Discontinue (a session of parliament)" .)