Reformulation of René's adroit justification for existence (6,5)

I believe the answer is:

raison detre

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'justification for existence' is the definition.
(I've seen this before)

'reformulation of rene's adroit' is the wordplay.
'rene's adroit' anagrams to 'RAISON D'ETRE'.
But, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for raison detre that I've seen before include "existing motive?" , "Reason for living" , "Justification for existence" , "Why one is" , "Purpose of existence" .)

I've seen this clue in The Guardian.

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