Fish from narrow waterways missing river (7)

I believe the answer is:

tenches

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'fish from narrow waterways missing river' is the definition.
I can't judge whether this definition defines the answer.

'fish from narrow waterways' is the wordplay.
'fish' becomes 'tench' (tench is a kind of fish).
'from' means one lot of letters go next to another.
'narrow waterways' becomes 'es' (I can't explain this - if you can you should believe this answer much more).
'tench'+'es'='TENCHES'

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I've seen this clue in The Guardian.

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