Book character (4)
I believe the answer is:
mark
This clue is a double definition.
'book' is the first definition.
(book of the Bible)
'character' is the second definition.
(thesaurus)
(Other definitions for mark that I've seen before include "Starting point in race" , "Smudge" , "Identify" , "follower of Jesus" , "What one might have paid old German" .)