Southern Native American rock formation (5)
I believe the answer is:
scree
'rock formation' is the definition.
'southern native american' is the wordplay.
'southern' becomes 's' (abbreviation).
'native american' becomes 'cree' (an indigenous people of North America).
's'+'cree'='SCREE'
(Other definitions for scree that I've seen before include "Debris at the foot of a cliff" , "Talus" , "loose stone" , "Mass of loose stones on mountainside" , "Sloping mass of rocks at the base of a cliff" .)