A long detailed story told sometimes in Shanghai (4)

I believe the answer is:

saga

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'a long detailed story' is the definition.
(I've seen this in another clue)

I can't explain the remainder of the clue.

(Other definitions for saga that I've seen before include "Account of great heroism" , "Body of legend" , "Chronicle; adventure" , "Flag associated with a" , "Long narrative" .)

I've seen this clue in The Irish Times.

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