Plains grazers (5)
I believe the answer is:
bison
'plains grazers' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bison that I've seen before include "Kind of shaggy cattle" , "North American buffalo" , "Buffalo (US)" , "Wild ox of the prairies" , "Large humped bovid of N America" .)