92 Jeep Cherokee numbers do not show up at night on the radio/clock. Sure its a bulb but solution to fixing is needed?
I would imagine the radio/clock has to be removed from the dash, partially dismantled and a new LED soldered in.
If the radio display is a LCD type then the backlight bulb may be burned out. This would require the radio to be removed and repairs done inside the radio. You may want to send it in to a shop for repair though it may be less expensive to just get a used radio from Ebay or a salvage yard. Check the connections in the rear of the radio and make sure the light circuit wires are connected as they should be.
My sons '95 Jeep had a problem with the LED display not working at all. These radios are prone to have bad solder joints on some of the surface mount resistors in the radio. After I resoldered the bad solder joint on one of the power resistors the display worked again.