Long way after English, unknown Portuguese greeting French author (5,4)
I believe the answer is:
emile zola
'french author' is the definition.
(I've seen this before)
'long way after english unknown portuguese greeting' is the wordplay.
'long way' becomes 'mile'.
'after' means one lot of letters go next to another.
'english' becomes 'e' (abbreviation).
'unknown' becomes 'z' (algebra).
'portuguese greeting' becomes 'ola' ('hello' in Portuguese).
'mile' put after 'e' is 'emile'.
'emile'+'z'+'ola'='EMILE ZOLA'
(Other definitions for emile zola that I've seen before include "novelist" , "Wrote J'Accuse in defence of Alfred Dreyfus" , ""Nana" author" , "French author" .)