Faulty account penned by fashionable clergyman (10)
I believe the answer is:
'faulty' is the definition.
(similar in meaning)
'account penned by fashionable clergyman' is the wordplay.
'account' becomes 'ac' (abbreviation for account).
'penned by' is an insertion indicator (inserted letters are penned in).
'fashionable' becomes 'in' (in can mean fashionable or trendy).
'clergyman' becomes 'curate' (curate is a kind of clergyman).
'ac' inserted within 'incurate' is 'INACCURATE'.
(Other definitions for inaccurate that I've seen before include "wrong" , "Unreliable" , "not hitting all the right notes?" .)