Undisputed big guns? Not after this story! (3,5,6)
I believe the answer is:
the great gatsby
'this story' is the definition.
(F Scott Fitzgerald novel)
'undisputed big guns? not' is the wordplay.
I cannot really understand how this works, but
'big' could be 'great' (synonyms) and 'great' is located in the answer.
'guns?' could be 'gats' (gat is a kind of gun) and 'gats' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'after' acts as a link.
Can you help me to learn more?
(Other definitions for the great gatsby that I've seen before include "F Scott Fitzgerald novel" , "classic work" , "Book" .)