"Nana" author (4)
I believe the answer is:
'nana author' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for zola that I've seen before include "French author of Germinal" , "See 15" , "19th-century French novelist" , "Emile --, French author" , "Fr. novelist (Germinal)" .)