The story of the comeback is a riot! (4)
I believe the answer is:
saga
'the story' is the definition.
(saga is a kind of story)
'the comeback is a riot' is the wordplay.
'the comeback' shows that the letters should be reversed in order.
'riot' becomes 'gas' (I can't explain this - if you can you should believe this answer much more).
'a'+'gas'='agas'
'agas' back-to-front is 'SAGA'.
'of' is the link.
Can you help me to learn more?
(Other definitions for saga that I've seen before include "Epic story" , "Epic - legend" , "Long and involved story" , "Long involved tale" , "Flag associated with a" .)