Yellowstone bovine (5)
I believe the answer is:
bison
'yellowstone bovine' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bison that I've seen before include "US wild ox" , "Kind of shaggy cattle" , "Wild cow" , "Large shaggy-maned animal" , "North American buffalo" .)