The most common and most likely answer to this crossword clue is the 13 letter word BEATIFICATION
I've seen this crossword clue in The Times
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More clues leading to the result BEATIFICATION
Buddy explains!
The straight part
We know that "Pope’s action" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pope’s action = beatification.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 BEATIFICATION mean?
BEATIFICATION noun- The act of beatifying, or the state of being beatified; especially, in the Roman Catholic Church, the act or process of ascertaining and declaring that a deceased person is one of "the blessed," or has attained the second degree of sanctity, — usually a stage in the process of canonization.