Change the name for greenhouse gas (7)
I believe the answer is:
methane
'for greenhouse gas' is the definition.
(I've seen this before)
'change the name' is the wordplay.
'change' indicates anagramming the letters.
'the'+'name'='thename'
'thename' anagrammed gives 'METHANE'.
(Other definitions for methane that I've seen before include "Naturally occurring flammable gas" , "Flammable gas, CH4" , "Marsh-gas" , "Firedamp" , "compound" .)