Pertaining to the eye (6)
I believe the answer is:
ocular
'pertaining to the eye' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ocular that I've seen before include "Eyepiece" , "Connected with vision (med.)" , "Glaucoma's such" , "Of the eye - visible" , "Viewer" .)