Pertaining to the eyes (6)
I believe the answer is:
ocular
'pertaining to the eyes' 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 "Of the eyes, visual" , "Connected with vision (med.)" , "Connected with the eyes or vision" , "connected with 23 [SIGHT]" , "not to be seen - due to this trouble?" .)