Learned books sustain latest paper supplier (9)
I believe the answer is:
newsagent
'paper supplier' is the definition.
(I've seen this before)
'learned books sustain latest' is the wordplay.
'learned' becomes 'sage' (both can mean wise).
'books' becomes 'nt' (New Testament).
'sustain' means one lot of letters go next to another (some letters carry or sustain others).
'latest' becomes 'new'.
'sage'+'nt'='sagent'
'sagent' put after 'new' is 'NEWSAGENT'.
(Other definitions for newsagent that I've seen before include "paper supplier" , "daily shop" , "shop selling rags?" , "place selling organs?" , "Shopkeeper selling magazines" .)