Bets off - that is one's closest friend (6)

I believe the answer is:

bestie

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'one's closest friend' is the definition.
I know nothing about this answer so I can't tell whether this works.

'bets off that is' is the wordplay.
'off' indicates an anagram.
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'bets' anagrammed gives 'best'.
'best'+'ie'='BESTIE'

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I've seen this clue in The Daily Express.

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