Introduction from Nora Ephron that takes the piss (7)

I believe the answer is:

nephron

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'the piss' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

'introduction from nora ephron' is the wordplay.
'introduction from' suggests taking the first letters.
The initial letter of 'nora' is 'n'.
'n'+'ephron'='NEPHRON'

'that takes' acts as a link.

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