It's long, wet, and not natural (5)

I believe the answer is:

canal

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'wet and not natural' is the definition.
I can't judge whether this defines the answer.

'it's long' is the wordplay.
'it's' becomes 'cana' (I can't explain this - if you can you should believe this answer much more).
'long' becomes 'l'.
'cana'+'l'='CANAL'

Can you help me to learn more?

(Other definitions for canal that I've seen before include "Inland waterway" , "Grand Union perhaps" , "Man-made watercourse" , "Man-made waterway" , "eg Grand Union" .)

I've seen this clue in the Evening Standard.

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