Fabulous writer regularly sampling mater’s soup (5)
I believe the answer is:
aesop
'fabulous writer' is the definition.
(writer of fables)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for aesop that I've seen before include "Ancient Greek author of moral tales" , "classic author" , "Fabulous man" , "Fabulous writer" , "Greek author of fables (c 620-560 BC)" .)