The most common and most likely answer to this crossword clue is the 12 letter word PRESBYTERIAN
I've seen this crossword clue in The Daily Telegraph
P
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The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PRESBYTERIAN mean?
PRESBYTERIAN adjective- Of or pertaining to a presbyter, or to ecclesiastical government by presbyters; relating to those who uphold church government by presbyters; also, to the doctrine, discipline, and worship of a communion so governed.