Biblical letter (7)
I believe the answer is:
epistle
'biblical letter' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for epistle that I've seen before include "Letter from a saint" , "Long formal letter (found in the New Testament?)" , "a for instance" , "(E.g. Paul's) letter" , "Letter, in the Bible perhaps" .)