Liquid and/or gas (5)
I believe the answer is:
radon
'gas' is the definition.
(radon is a gas)
'liquid andor' is the wordplay.
'liquid' indicates an anagram.
'andor' anagrammed gives 'RADON'.
(Other definitions for radon that I've seen before include "Inert gas that occurs naturally" , "Naturally occurring inert gas" , "Colourless gas, atomic number 86" , "Noble gas, Rn" , "hazardous substance" .)