Extremely green water coming up street (7)

I believe the answer is:

naivest

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'extremely green water coming up street' is the definition.
I can't judge whether this definition defines the answer.

'water coming up street' is the wordplay.
'water' becomes 'evian' (mineral water brand).
'coming up' says the letters should be written backwards (in a down clue, letters go up).
'street' becomes 'st' (abbreviation).
'evian' backwards is 'naive'.
'naive'+'st'='NAIVEST'

Can you help me to learn more?

(Other definitions for naivest that I've seen before include "very green" , "Most simple" , "Least sophisticated" , "Most unsophisticated" , "Most open" .)

I've seen this clue in The Independent.

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