Release a Parisian philosopher, guillotine finally spared (6)
I believe the answer is:
unlock
'release' is the definition.
(thesaurus)
'a parisian philosopher guillotine finally spared' is the wordplay.
I cannot quite see how this works, but
'a parisian' could be 'un' and 'un' is present in the answer.
The remaining letters 'lock' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for unlock that I've seen before include "Release with a key" , "Crop" , "Release bolt" , "Open with key" .)