Element below neon on the periodic table
I believe the answer is:
argon
'element below neon on the periodic table' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for argon that I've seen before include "Gas, 1% of atmosphere" , "Organ (anag.)" , "Noble gas used in light bulbs" , "An insert gas to groan about" , "Noble gas, Ar" .)