Point grasped by star American historian (9)
I believe the answer is:
herodotus
'historian' is the definition.
(I know that Herodotus is a historian)
'point grasped by star american' is the wordplay.
'point' becomes 'dot' (synonyms).
'grasped by' is an insertion indicator (I've seen this in other clues).
'star' becomes 'hero' (both can mean a main character).
'american' becomes 'us' (abbreviation for United States).
'hero'+'us'='herous'
'dot' inserted into 'herous' is 'HERODOTUS'.
(Other definitions for herodotus that I've seen before include "Historical pioneer" , "Ancient Greek historian" , "Old Greek" , "Famous Greek" .)