A certain something (2,2,4,4)

I believe the answer is:

je ne sais quoi

(Other definitions for je ne sais quoi that I've seen before include "Something indescribable (French)" , "Quality or thing that's hard to describe" , "Quality that can't be easily described" , "(A certain) something" , "Indefinable quality" .)

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.