Son plugging heroic work by foreign-sounding churchgoer (12)
I believe the answer is:
episcopalian
'churchgoer' is the definition.
(member of the Episcopal Church)
'son plugging heroic work by foreign-sounding' is the wordplay.
I cannot quite see how this works, but
'son' could be 's' (genealogical abbreviation for son) and 's' is found in the answer.
'heroic' could be 'epic' (synonyms) and 'epic' is located in the leftover letters.
'work' could be 'op' (abbreviation for opus) and 'op' is located in the answer.
This explanation may well be incorrect...
(Another definition for episcopalian that I've seen is " Member of a certain church".)