Offence by Church concerning devout (7)
I believe the answer is:
sincere
'devout' is the definition.
('sincere' can be similar in meaning to 'devout')
'offence by church concerning' is the wordplay.
'offence' becomes 'sin' (I've seen this before).
'by' means one lot of letters go next to another.
'church' becomes 'ce' (abbreviation for Church of England).
'concerning' becomes 're'.
'sin'+'ce'+'re'='SINCERE'
(Other definitions for sincere that I've seen before include "like informal correspondents?" , "Showing genuine feelings" , "Unfeigned, genuine" , "Pure" , "Not hypocritical" .)