What is one who upholds or supports that which props; one who, or that which, stays, stops, or restrains; also, colloquially, a horse, man, etc., that has endurance, an a race called?

stayer — One who upholds or supports that which props; one who, or that which, stays, stops, or restrains; also, colloquially, a horse, man, etc., that has endurance, an a race. (Webster's 1913.)