Write about horn-shaped unit of the kidney (7)

I believe the answer is:

nephron

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'unit of the kidney' is the definition.
The answer and definition can be both body parts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

'write about horn-shaped' is the wordplay.
'write' becomes 'pen' (synonyms).
'about' says the letters should be written backwards.
'shaped' indicates an anagram.
'pen' backwards is 'nep'.
'horn' anagrammed gives 'hron'.
'nep'+'hron'='NEPHRON'

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I've seen this clue in The Hindu.

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