Truthfulness of account given by member of the clergy's office (8)
I believe the answer is:
accuracy
'truthfulness of account' is the definition.
'accuracy' can be an answer for 'truthfulness' (I've seen this before). I am not certain of the 'of account' bit.
'given by member of the clergy's office' is the wordplay.
'given by' is a charade indicator (letters next to each other).
'member of the clergy's' becomes 'ac' (I can't justify this - if you can you should believe this answer much more).
'office' becomes 'curacy' (curacy is a kind of office).
'ac'+'curacy' is 'ACCURACY'.
Can you help me to learn more?
(Other definitions for accuracy that I've seen before include "Precision of detail" , "Absolute correctness" , "Truthfulness" , "faithfulness" , "Preciseness" .)