Student of optics? (5)
I believe the answer is:
pupil
This clue could be a double definition.
'student' is the first definition.
(pupil can mean a student at a school)
'optics?' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'of' is the link.
Can you help me to learn more?
(Other definitions for pupil that I've seen before include "Schoolboy or eye part" , "One studying" , "The sort of student" , "One being taught" , "bit of a looker" .)