Gas surprisingly clean yet ultimately non-renewable (9)
I believe the answer is:
acetylene
'gas' is the definition.
(acetylene is a gas)
'surprisingly clean yet ultimately non-renewable' is the wordplay.
I cannot really see how this works, but
an anagram of 'yet' is 'ety' which is located in the answer.
an anagram of 'clean' is 'aclen' which is located in the left over letters.
A single letter 'e' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for acetylene that I've seen before include "Gas used chiefly in welding" , "Illuminating stuff also used for joining" , "powers industrial torch" , "Flammable gas" , "cutting gas emission?" .)