Crossword Genius

One may look through this French town (4)

Ross

I believe the answer is:

lens

This clue is a double definition.

'one may look through this' is the first definition.
(eg a glasses lens)

'french town' is the second definition.
(town in northern France)

(Other definitions for lens that I've seen before include "Optical refractor" , "One could project a picture" , "Photographer's accessory" , "Refracting device" , "Focussing glass" .)

I've seen this clue in The Times.
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