You may be able to remove the potentiometer from the board, fold back the tabs to disassemble. Clean everything up with ISO, glue and/or secure the slide fingers back to the nylon block (which is most likely the culprit). As long as the carbon tracks and/or fingers aren't destroyed you might get it working again. If the carbon track has a crack you can check resistance with a volt meter to find it (if not obvious) and repair it with a conductive paste.
Obviously the easier solution would be to find a working replacement. Someone here might very well have one.