Abolish America's donut, flatly (7)

I believe the answer is:

annulus

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'donut flatly' is the definition.
I can't tell whether this definition defines the answer.

'abolish america's' is the wordplay.
'abolish' becomes 'annul' (I've seen this before).
'america's' becomes 'US'' ('US' can be a synonym of 'america').
'annul'+'us'='ANNULUS'

Can you help me to learn more?

(Other definitions for annulus that I've seen before include "Ring-shaped object" , "Ring-shaped structure" .)

I've seen this clue in The Independent.

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