I've never ridden a horse, so I'm perhaps missing that context for this fragrance that everyone else seems to be catching.
However this is the smell of a personality, and an experience.
You're getting into this older model pickup, and the driver has just reached over to pull up the door lock to let you in. You hear "seven year ache" by Rosanne Cash on the radio, as you slide onto the leather bench seat you notice the driver is wearing a plaid shirt with a new light tan lined leather vest, his jeans held up with a brand new, large-buckled leather belt and are tucked into his new leather boots because he's been stamping around doing work in the animal pen, which you also smell from the blanket tucked into the seat behind you. You can also tell from the smell of his clothes that the driver smokes cigarettes, but not in the truck. You next see a can of wintergreen dip on seat between you both, and you can smell that the driver already has a pinch between his lip and jaw.