The Raven's author rewrote a true tale for Betjeman, say (4,8)
I believe the answer is:
poet laureate
'the raven's author' is the definition.
'Poet Laureate' can be an answer for 'author' (Poet Laureate is an example). I'm unsure of the 'the raven's' bit.
'rewrote a true tale for betjeman say' is the wordplay.
'rewrote' is an anagram indicator (I've seen this in other clues).
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'betjeman say' becomes 'poe' (I am not sure about this - if you are sure you should believe this answer much more).
'a'+'true'+'tale'='atruetale'
'atruetale' anagrammed gives 'tlaureate'.
'tlaureate' after 'poe' is 'POET LAUREATE'.
Can you help me to learn more?
(Other definitions for poet laureate that I've seen before include "Court versifier" , "Motion or Duffy, for example" , "such as Tennyson" , "Official versifier" , "Wordsworth, for instance" .)