Little Leonard's optical device (4)

I believe the answer is:

lens

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'optical device' is the definition.
(lens is a kind of optical device)

'little leonard's' is the wordplay.
'little' becomes 'l' (abbreviation for little).
'leonard' becomes 'ens' (I can't explain this - if you can you should give a lot more credence to this answer).
'l'+'ens'='LENS'

Can you help me to learn more?

(Other definitions for lens that I've seen before include "Device to converge or diverge light" , "Bit of a looker" , "Camera component" , "Light-focusing device" , "Part of the inner eye, or camera" .)

I've seen this clue in the Sydney Morning Herald.

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