Sight-related (5)
I believe the answer is:
optic
'sight-related' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for optic that I've seen before include "Picot (anag.)" , "Pub drinks dispenser" , "Spirit measuring device" , "Pertaining to sight" , "Spirits dispenser" .)