An account of the New Testament (9)
I believe the answer is:
statement
'an account' is the definition.
(I've seen this before)
'new testament' is the wordplay.
'new' indicates an anagram.
'testament' anagrammed gives 'STATEMENT'.
'of the' acts as a link.
(Other definitions for statement that I've seen before include "Financial summary" , "Formal account given to police" , "It's made, about account say" , "Assertion" , "Account given to a court" .)