First of all, I personally dont know of any front wheel drive cars that have a "fan belt" let alone one that slips so thats definitely not the problem.
Powersteering pumps generally only "grind" while making turns, and if one is bad enough to grind while driving straight, its definitely bad enough to grind while sitting at idle.
The issue is not the suspension either as none of the suspension parts or mounts move/ articulate at the speed of the vehicle.
The best guess based on your vague description is most likely going to be wheel bearing on its way out, fairly inexpensive fix.