Take a hike in Native American territory's western part (3,2)
I believe the answer is:
hop it
'take a hike' is the definition.
(both are used to tell someone to go away)
'native american territory's western part' is the wordplay.
'native american' becomes 'hopi' (the Hopi are a Native American people).
'western part' suggests taking the first letters (the rightmost or westernmost end of the word).
The initial letter of 'territory' is 't'.
'hopi'+'t'='HOP IT'
'in' acts as a link.
(Other definitions for hop it that I've seen before include "Skedaddle!" , "Scarper, be gone" , "Run along now!" , "split" , "Leave" .)