I agree with 4wd. That "clear filter" is a lens cap. Just unscrew it and wash it if you need to. The part the actual lens looks through is plastic so don't try to wipe it clean while dry or it could get scratched.
I think the concept is pretty genius. A lens cap that can be unscrewed and replaced by whatever photo filter you want. Somebody will figure that out and make them. Probably already have.