Yes it can be cleaned. You can dampen a paper towel with window cleaner and wipe the screen. Just dampen the towel though not too wet. That way no excess liquid can get into the phone. If there is stuff under the screen you may be able to remove the protector and clean it, staying away from the adhesive parts, so it will stick back on when clean.

The screen protectors stick using static. So just use water to rinse it off and let it dry off don't wipe it clean or it will go worse.

1. Cool(secret) the protective film in the refrigerator for a few hours to cool it down and to make the adhesive less sticky when you install it.
2. Wash your hands with soap & water, drying carefully. Oil from your skin will mess up the installation.
3. Peel back just a corner of the clear plastic with your fingernail.
4. Dampen your screen with a little distilled or filtered water.
5. Pull a small area from one edge of the protector.
6. Align one sticky edge of the plastic film with your LCD screen.
7. Pull the plastic along the LCD screen, removing the backing, slowly.
8. Use a plastic credit card to smooth out any bubbles. (the water helps keep the plastic from sticking too soon.
9. Smooth out imperfections with fingertips and credit cards.
10. Dry the excess moisture with a soft cloth.
11. You may still rub out wrinkles and bubbles with your fingers for a while until the adhesive warms up.