Native American restricted set of beliefs (4)
I believe the answer is:
cree
'native american' is the definition.
(an indigenous people of North America)
'restricted set of beliefs' is the wordplay.
'restricted' means to remove the last letter (restricted can mean limited or reduced).
'set of beliefs' becomes 'creed' (I've seen this in another clue).
'creed' with its final letter taken away is 'CREE'.
(Other definitions for cree that I've seen before include "Native American tribe/language" , "North American native" , "Native American; rhymes with French cheese" , "tribe" , "American Indians" .)