Optical component; city of northern France (4)

I believe the answer is:

lens

(Other definitions for lens that I've seen before include "Part of telescope" , "Aid for viewing" , "Part of the inner eye, or camera" , "City of northern France: periscope part" , "Focussing device" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.