Endorse south with north in conflict (8)
I believe the answer is:
sanction
'endorse' is the definition.
(I know that endorse is a more specific form of sanction)
'south with north in conflict' is the wordplay.
'south' becomes 's' (abbreviation).
'with' means one lot of letters go next to another.
'north' becomes 'N' (abbreviation).
'in' indicates putting letters inside.
'conflict' becomes 'action' (action can mean action in war).
'n' inserted into 'action' is 'anction'.
's'+'anction'='SANCTION'
(Other definitions for sanction that I've seen before include "coercive measure" , "Give final permission" , "Official permission or authority" , "punitive action" , "Ratification" .)