Type of element (4,5)
(Other definitions for gas that I've seen before include "Eg, oxygen" , "eg CO2" , "natural resource" , "16 (US)" , "Oxygen is one" .)
'type of element' is the definition.
This is all the clue.
(Other definitions for metal that I've seen before include "Copper or silver, say" , "Intrinsic quality; stone for roads" , "Eg, copper" , "Alloy" , "Broken stone used in road-making" .)
'type of element' is the definition.
This is all the clue.
(Other definitions for rare earth that I've seen before include "metallic element" , "Oxide" , "Particular element" , "discovery in Ytterby?" , "One of a group of 15 hard to distinguish elements - at her rear (anag)" .)