Faithful account by clergyman (8)
I believe the answer is:
accurate
'faithful' is the definition.
(similar in meaning)
'account by clergyman' is the wordplay.
'account' becomes 'ac' (abbreviation for account).
'by' means one lot of letters go next to another.
'clergyman' becomes 'curate' (assistant to a priest).
'ac'+'curate'='ACCURATE'
(Other definitions for accurate that I've seen before include "Precise and exact (8)" , "Spot on" , "Correct, free of error" , "Precise, correct" , "strict" .)