The most common and most likely answer to this crossword clue is the 13 letter word PHILOSOPHICAL
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result PHILOSOPHICAL
Buddy explains!
The straight part
We know that "resigned" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case resigned = philosophical.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 PHILOSOPHICAL mean?
PHILOSOPHICAL adjective- Of, or pertaining to, philosophy.
- Rational; analytic or critically-minded; thoughtful.
- Detached, calm, stoic.