Eye covering

LID

It’s what blinks to protect and moisten the part that sees.

"Eye covering" is a straightforward clue pointing to the part of the eye that opens and closes. The answer is "LID," which is the thin, movable skin that protects the eye when shut. There’s no wordplay here—it’s a direct definition, making it an easy fill for solvers familiar with basic anatomy. Think of blinking, and you’ve got it.