US writer ruins platonic arrangement (5,8)

I believe the answer is:

upton sinclair

'us writer' is the definition.
(US novelist, 1878-1968)

'ruins platonic arrangement' is the wordplay.
'arrangement' indicates anagramming the letters.
'ruins'+'platonic'='ruinsplatonic'
'ruinsplatonic' with letters rearranged gives 'UPTON SINCLAIR'.

I've seen this clue in The Guardian.

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