Binoculars part (4)
I believe the answer is:
lens
'binoculars part' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lens that I've seen before include "Part of telescope" , "Dark cloud; shining light" , "Optical refractor" , "Photographer's accessory" , "Part of the inner eye, or camera" .)