Rebel is pressing to capture north (9)
I believe the answer is:
insurgent
'rebel' is the definition.
('insurgent' can be a synonym of 'rebel')
'is pressing to capture north' is the wordplay.
'pressing' becomes 'urgent' ('urgent' can be a synonym of 'pressing'**).
'to capture' indicates putting letters inside.
'north' becomes 'n' ('N' can be a synonym of 'north').
'is'+'urgent'='isurgent'
'isurgent' enclosing 'n' is 'INSURGENT'.
(Other definitions for insurgent that I've seen before include "Unresting like a rebel" , "Revolting" , "rising" , "Rebel, revolutionary" , "freedom fighter" .)