6 down
Barrier
dropped
to
protect
pupil
(6)
Barrier dropped to protect pupil (6)
hints
0
checks
0
hints
The whole clue is the definition (& lit or double definition).
How the clue works
Look at the whole clue — it's both the definition and the wordplay working together. A barrier that drops to protect your pupil is exactly what an eyelid does. The charade builds it up piece by piece: EYE gives you the pupil, and LID is your barrier, and you just stick them together.