The most common and most likely answer to this crossword clue is the 6 letter word SARTRE
I've seen this crossword clue in The Guardian
S
A
R
T
R
E
More clues leading to the result SARTRE
- Reject a lot of rubbish about writer and philosopher
- Somewhat pert rascal upset philosopher
- Writer’s skill showcased in series regularly
- Philosopher right to stop one abandoning use of irony
- Special skill concerning French thinker
- Arrest criminal John-Paul!
- Jean-Paul‘s wrongful arrest
- Fiddle string: rare device for writer
- Rarest sort of philosopher
- Wrongly arrest existentialist
Buddy explains!

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.