Layer backs a horse for example (6)

I believe the answer is:

lamina

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'layer' is the definition.
(I've seen this before)

'backs a horse for example' is the wordplay.
'backs' says the letters should be written backwards.
'a' becomes 'an'.
'horse for example' becomes 'imal' (I can't justify this - if you can you should give a lot more credence to this answer).
'an'+'imal'='animal'
'animal' reversed gives 'LAMINA'.

Can you help me to learn more?

(Other definitions for lamina that I've seen before include "Thin plate or layer" , "Flat plate" , "Thin plate or scale" .)

I've seen this clue in The Globe and Mail.

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