Letters record dreadful lies about saint (8)
I believe the answer is:
epistles
'letters' is the definition.
(I know this)
'record dreadful lies about saint' is the wordplay.
'record' becomes 'ep' (abbreviation for extended play record).
'dreadful' indicates an anagram.
'about' is an insertion indicator.
'saint' becomes 'st' (abbreviation).
'lies' anagrammed gives 'iles'.
'iles' going around 'st' is 'istles'.
'ep'+'istles'='EPISTLES'
(Other definitions for epistles that I've seen before include "Biblical letters" , "Letters, missives" , "It sleeps among letters of the Apostles" , "Long communications" .)