Helium or krypton, eg (5,3)
I believe the answer is:
noble gas
I believe this is a double definition.
'helium' is the first definition.
(I've seen this before)
'krypton eg' is the second definition.
(I know that Kr is a type of noble gas)
(Other definitions for noble gas that I've seen before include "He symbolises one" , "Such as helium or neon" , "One of argon, neon etc." , "such as no. 2 in the table" , "Such as, eg, radon or neon" .)