Most talented new books (3,9)
I believe the answer is:
old testament
'books' is the definition.
(books of the Bible)
'most talented new' is the wordplay.
'new' indicates anagramming the letters.
'most'+'talented'='mosttalented'
'mosttalented' is an anagram of 'OLD TESTAMENT'.
(Other definitions for old testament that I've seen before include "Modest talent (anag.)" , "Books" , "Genesis, Exodus etc" , "religious work" , "Job, for example, to be found here" .)