I wreckon maybe a wheel bearing is dry. Break application will stop the squeak some times as it assists the wheel running truer as the rotor gets pinched between the pads...
Mine has developed a tiny sqeak in the front right. When I apply the breaks it stops. I only hear it at about 50 to 60 Ks then it stops as the spead builds up or I apply breaks. Smidgeon of play in that wheel when the car is jacked up...
Do what GOJEEP said there should not be even an incy wincy tiny weeny bit of play at all. My play is slow slight you can hardly detect it *BUT* it is there and it is the bearing warn and drying up.
Have a gig at the link below:
http://www.off-road.com/jeep/cheroke...ing/index.html