Incredible French one ready in Rio? (6)

I believe the answer is:

unreal

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'incredible' is the definition.
(thesaurus)

'french one ready in rio?' is the wordplay.
'french one' becomes 'un' ('one' in French).
'ready in rio?' becomes 'real' (I can't explain this - if you can you should give a lot more credence to this answer).
'un'+'real'='UNREAL'

Can you help me to learn more?

(Other definitions for unreal that I've seen before include "Dreamlike" , "Not actual or credible" , "fake" , "Artificial, insubstantial" , "Not true to life" .)

I've seen this clue in The Times.

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