Crossword Genius

Thin layer impaired by lines at first (7)

Ross

I believe the answer is:

lamella

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'thin layer' is the definition.
(I've seen this in another clue)

'impaired by lines at first' is the wordplay.
'impaired by' becomes 'lame' (I can't explain this - if you can you should believe this answer much more).
'lines' becomes 'll' (an abbreviation for line written twice).
'at first' becomes 'a' (lst letter of 'at').
'lame'+'ll'+'a'='LAMELLA'

Can you help me to learn more?

(Another definition for lamella that I've seen is " Thin plate".)

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