Endurance shown by southern army besieging dictator (7)
I believe the answer is:
stamina
'endurance' is the definition.
(stamina is a kind of endurance)
'southern army besieging dictator' is the wordplay.
'southern' becomes 's' (abbreviation).
'army' becomes 'ta' (abbreviation for Territorial Army).
'besieging' means one lot of letters goes inside another.
'dictator' becomes 'amin' (I have seen 'Brutal dictator' mean 'amin' so perhaps 'dictator' could also mean 'amin').
'ta' placed around 'amin' is 'tamina'.
's'+'tamina'='STAMINA'
'shown by' acts as a link.
(Other definitions for stamina that I've seen before include "Vigour" , "Staying-power, endurance" , "Parts of flowers" , "The ability to sustain prolonged physical or mental effort" , "Energy and staying power" .)