French existentialist philosopher (6)
I believe the answer is:
sartre
'french existentialist philosopher' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sartre that I've seen before include "French philosopher, 1905-80" , "Jean-Paul -, French philosopher/author" , "Jean Paul . . ., French existentialist writer" , "Sooner" , "French philosophic writer" .)