A feature of Saturn, it emits a flame (3,4)
I believe the answer is:
gas ring
'it emits a flame' is the definition.
The definition suggests a singular noun which matches the answer.
'a feature of saturn' is the wordplay.
I cannot quite see how this works, but
'a' is found in the answer.
'feature of saturn' could be 'ring' (I've seen this in another clue) and 'ring' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for gas ring that I've seen is " Saucepan heater".)