Krypton, for one (4,3)
'krypton for one' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rare gas that I've seen before include "Element such as helium, neon etc" , "Eg, helium or neon" , "Such as argon or xenon" , "Such as neon, argon, etc" .)
'krypton for one' is the definition.
(I know that Kr is a type of noble gas)
This is all the clue.
(Other definitions for noble gas that I've seen before include "Such as helium or neon" , "One of argon, neon etc." , "such as no. 2 in the table" , "Such as, eg, radon or neon" , "He symbolises one" .)