* It spoils long-dead queen (8)

I believe the answer is:

marsanne

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'it spoils' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'long-dead queen' is the wordplay.
'long dead' becomes 'mars' (I can't explain this - if you can you should believe this answer much more).
'queen' becomes 'anne' (Queen Anne, m8th-century queen).
'mars'+'anne'='MARSANNE'

Can you help me to learn more?

(Another definition for marsanne that I've seen is " Grape variety".)

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

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