Name the new gas (7)
I believe the answer is:
methane
'gas' is the definition.
(methane is a gas)
'name the new' is the wordplay.
'new' is an anagram indicator.
'name'+'the'='namethe'
'namethe' is an anagram of 'METHANE'.
(Other definitions for methane that I've seen before include "Get fuel" , "Main constituent of natural gas" , "contributor to global warming" , "Flammable gas, CH4" , "compound" .)