Fabulous Greek author (5)
I believe the answer is:
aesop
This clue is a double definition.
'fabulous greek' is the first definition.
(I've seen this in another clue)
'author' is the second definition.
(I've seen this before)
(Other definitions for aesop that I've seen before include "his writings were fabulous" , "Greek fabulist (Tortoise and the Hare)" , "So ape the writer of fables" , "Greek author, famous for his fables" , "he wrote in Greek" .)