Devout transgress about to embrace church (7)
I believe the answer is:
sincere
'devout' is the definition.
(similar in meaning)
'transgress about to embrace church' is the wordplay.
'transgress' becomes 'sin' (sinning is a kind of transgressing).
'about' becomes 're' ('re' means regarding or about).
'to embrace' indicates putting letters inside.
'church' becomes 'CE' (abbreviation for Church of England).
'sin'+'re'='sinre'
'sinre' enclosing 'ce' is 'SINCERE'.
(Other definitions for sincere that I've seen before include "Free from deception" , "Open and genuine, not deceitful" , "straightforward" , "Genuine; deceit-free" , "Without deceit, genuine" .)