Books we sent out with positive response time after time (3,9)
I believe the answer is:
new testament
'books' is the definition.
(I have seen 'Sacred books' mean 'new testament' so perhaps 'books' could also mean 'new testament')
'we sent out with positive response time after time' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'with positive response time' becomes 'ament' (I can't explain this - if you can you should believe this answer much more).
'after' is a charade indicator (letters next to each other).
'time' becomes 't'.
'we'+'sent'='wesent'
'wesent' with letters rearranged gives 'newtes'.
'ament' put after 't' is 'tament'.
'newtes'+'tament'='NEW TESTAMENT'
Can you help me to learn more?
(Other definitions for new testament that I've seen before include "Holy Writ" , "religious work" , "Sacred books" , "collection of religious books" , "Canon" .)