Rebel in south, pressing (9)
I believe the answer is:
insurgent
'rebel' is the definition.
('insurgent' can be a synonym of 'rebel')
'in south pressing' is the wordplay.
'south' becomes 's' ('S' can be a synonym of 'south').
'pressing' becomes 'urgent' ('urgent' can be a synonym of 'pressing').
'in'+'s'+'urgent'='INSURGENT'
(Other definitions for insurgent that I've seen before include "rising" , "freedom fighter" , "Unresting like a rebel" , "Revolting" , "Rebel, revolutionary" .)