Constant love in vigil over Native American (7)
I believe the answer is:
choctaw
'native american' is the definition.
(I know that Choctaw is a type of Muskhogean)
'constant love in vigil over' is the wordplay.
'constant' becomes 'C' (mathematical abbreviation).
'love' becomes 'o' (love means zero in tennis).
'in' is an insertion indicator.
'vigil' becomes 'watch' (synonyms).
'over' says the letters should be written in reverse.
'o' put inside 'watch' is 'watcoh'.
'watcoh' back-to-front is 'hoctaw'.
'c'+'hoctaw'='CHOCTAW'
(Other definitions for choctaw that I've seen before include "Native American - skating movement - cat chow (anag)" , "Brave" , "skating move" , "figure-skating manoeuvre" , "North American Indian" .)