On reflection ultimately calamitous, U.K. to consume excessively American puzzles (7)

I believe the answer is:

sudokus

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'puzzles' is the definition.

'on reflection ultimately calamitous u k to consume excessively american' is the wordplay.
'on reflection' is a reversal indicator.
'ultimately' indicates one should take the final letters.
'to consume excessively' becomes 'od' (I can't explain this - if you can you should believe this answer much more).
'american' becomes 'US' (United States).
The last letter of 'calamitous' is 's'.
's'+'u'+'k'+'od'+'us'='sukodus'
'sukodus' written backwards gives 'SUDOKUS'.

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I've seen this clue in The Guardian.

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