Crossword Genius

Argon or neon, eg (5,3)

Ross

I believe the answer is:

inert gas

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This clue could be a double definition.

'argon' is the first definition.
The answer and definition can be both substances as well as being singular nouns.
Maybe there's an association between them I don't understand?

'neon eg' is the second definition.
(I know that neon is a type of inert gas)

'or' is the link.

Can you help me to learn more?

(Other definitions for inert gas that I've seen before include "Eg, krypton or argon" , "He perhaps" , "He, amongst others" , "Passive element in the helium group" , "Eg, helium or argon" .)

I've seen this clue in The Times.
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