Countries together resolve southern troubles (9)
I believe the answer is:
unsettles
'troubles' is the definition.
(unsettle can mean to trouble or disturb)
'countries together resolve southern' is the wordplay.
'countries together' becomes 'UN' (United Nations).
'resolve' becomes 'settle' (settling is a kind of resolving).
'southern' becomes 's' (abbreviation).
'un'+'settle'+'s'='UNSETTLES'
(Other definitions for unsettles that I've seen before include "Disturbs" , "causes disturbance" .)