What can you do if your central air has water condensing all over but the drain going outside is clear?

Depending on your installation, I'd say two things: either your condensate drain pipe is clogged, or it does not have the proper pitch and is not draining by gravity. (Or if you have a condensate pump, it's not working) Sounds like you may have a loose or missing piece of insulation on the inside of the unit and the exterior of the cabinet/ductwork is getting too cold and is sweating as a result.