Author Bellow (4)
I believe the answer is:
'author bellow' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for saul that I've seen before include "Predecessor of King David" , "Oratorio by Handel" , "Bellow was one" , "-- Bellow, Nobel-winning author" , "- - of Tarsus" .)