What's often spliced in macabre fiction (9)

I believe the answer is:

mainbrace

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'fiction' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?

'what's often spliced in macabre' is the wordplay.
'in macabre' anagrams to 'MAINBRACE'.
However, I am not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for mainbrace that I've seen before include "It's spliced aboard" , "that got spliced" , "may get spliced at sea" , "rope" , "Part of rigging" .)

I've seen this clue in the Sydney Morning Herald.

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