Returning a type of element? Long story (4)

I believe the answer is:

saga

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'long story' is the definition.
(a saga is a long and complicated story)

'returning a type of element?' is the wordplay.
'returning' shows that the letters should be reversed in order.
'type of element?' becomes 'gas' (I can't justify this - if you can you should give a lot more credence to this answer).
'a'+'gas'='agas'
'agas' back-to-front is 'SAGA'.

Can you help me to learn more?

(Other definitions for saga that I've seen before include "Long heroic, family, story" , "Soap opera" , "Body of legend" , "Old story" , "Epic - legend" .)

I've seen this clue in The Daily Express.

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