Relation of audiobook version of Zola novel? (5)

I believe the answer is:

nanna

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'relation' is the definition.
(I know that nanna is a type of relation)

I can't explain the rest of the clue.

(Other definitions for nanna that I've seen before include "Child's grandmother" , "Pet name for a grandmother" , "Senior woman" , "Grandmother (colloquial)" , "Mother's mother?" .)

I've seen this clue in The Guardian.

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