Possible Clues:

• Abbr. in a beach bag
• It prevents burn out: Abbr.
• Sunblock-bottle letters
• Lotion abbr.
• Letters on a bottle at the beach
• If you're fair, you might want a high one
• Lotion no.
• Effectiveness of a coat at the beach?: Abbr
• Ray-blocking letters
• Sunscreen-tube letters