Fable writer (5)
I believe the answer is:
'fable writer' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for aesop that I've seen before include "Greek author of fables (c 620-560 BC)" , "Greek fabulist (Tortoise and the Hare)" , "fabulous figure?" , "Author of many fables" , "Greek storyteller" .)