It's beneath xenon in the periodic table (5)

I believe the answer is:

radon

(Other definitions for radon that I've seen before include "Inert gas - adorn (anag)" , "Naturally occurring inert gas" , "A radioactive gas, symbol Rn" , "Colourless gas, atomic number 86" , "Natural gas considered a hazard to health" .)

I've seen this clue in The Wall Street Journal.

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.