The most common and most likely answer to this crossword clue is the 13 letter word METAPHYSICIAN
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result METAPHYSICIAN
Buddy explains!
The straight part
We know that "Philosopher" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case philosopher = metaphysician.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 METAPHYSICIAN mean?
METAPHYSICIAN noun- A philosopher who specializes in the scholarly study of metaphysics.