Guard southern access point (6)
I believe the answer is:
sentry
'guard' is the definition.
(sentry is a kind of guard)
'southern access point' is the wordplay.
'southern' becomes 's' (abbreviation).
'access point' becomes 'entry' (I've seen this before).
's'+'entry'='SENTRY'
(Other definitions for sentry that I've seen before include "Mil. guard" , "One keeps guard" , "Soldier posted to keep watch" , "One keeps watch" , "Picket" .)