Encountered Warne dismissing opener for gas (7)
I believe the answer is:
methane
'for gas' is the definition.
(methane is a gas)
'encountered warne dismissing opener' is the wordplay.
I cannot really understand how this works, but
'encountered' could be 'met' ('meet' can be a synonym of 'encounter') and 'met' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for methane that I've seen before include "Main constituent of natural gas" , "Get fuel" , "Naturally occurring flammable gas" , "Main component of natural gas" , "simplest hydrocarbon" .)