Carstone’s eccentric forebears (9)
I believe the answer is:
ancestors
'forebears' is the definition.
(one's forebears are one's ancestors)
'carstone's eccentric' is the wordplay.
'eccentric' is an anagram indicator.
'carstones' anagrammed gives 'ANCESTORS'.
(Other definitions for ancestors that I've seen before include "They have gone before us" , "Forebears" , "Antecedents" .)