Is it good as fuel? (3)
I believe the answer is:
gas
'fuel?' is the definition.
(gas is a kind of fuel)
'is it good as' is the wordplay.
I cannot really see how this works, but
'good' could be 'g' (abbreviation) and 'g' is located in the answer.
'as' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for gas that I've seen before include "Neon, for example" , "In brief, American petrol" , "chew the fat" , "Fumes, vapour" , "Idle chat" .)