Account by cleric with no mistakes (8)
I believe the answer is:
accurate
'with no mistakes' is the definition.
(completely accurate or correct)
'account by cleric' is the wordplay.
'account' becomes 'ac' (abbreviation).
'by' means one lot of letters go next to another.
'cleric' becomes 'curate' (I've seen this before).
'ac'+'curate'='ACCURATE'
(Other definitions for accurate that I've seen before include "Meticulous" , "Correct, right" , "Totally correct" , "Correct in all details" , "telling it like it is" .)