Money invested in genuine trimmed light sensor (6)
I believe the answer is:
retina
'light sensor' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'money invested in genuine trimmed' is the wordplay.
'money' becomes 'tin' (old-fashioned slang term for money).
'invested in' means one lot of letters goes inside another.
'genuine' becomes 'real' (associated in meaning).
'trimmed' means to remove the last letter (the last letter is trimmed off).
'real' with its last letter removed is 'rea'.
'tin' going within 'rea' is 'RETINA'.
Can you help me to learn more?
(Other definitions for retina that I've seen before include "What's behind the humour" , "Viewer's part" , "Membrane covering the back of the eyeball" , "Light-sensitive eye layer" , "Light-sensitive membrane of the eyeball" .)