Jean-Paul Sartre’s deep discomfort? (3,2,3)
I believe the answer is:
mal de mer
'deep discomfort?' is the definition.
(French for seasickness, discomfort with 'the deep')
'jean-paul sartre's' is the wordplay.
I cannot quite understand how this works, but
'paul' could be 'me' (where the crossword setter is 'Paul') and 'me' is found within the answer.
This explanation may well be incorrect...
(Other definitions for mal de mer that I've seen before include "Seasickness (French)" , "type of sickness" , "problem on board" .)