Source of ancient fables (5)
I believe the answer is:
aesop
'source of ancient fables' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aesop that I've seen before include "A pose by Greek writer of fables" , "Ancient Greek fabulist" , "Author of many fables" , "Greek author, famous for his fables" , "Greek author of fables (c 620-560 BC)" .)