They keep water out as well as looking different (3,5)

I believe the answer is:

sea walls

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'they keep water out' is the definition.
I know nothing about this answer so I can't judge whether this works.

'as well as looking different' is the wordplay.
'looking different' indicates an anagram (I've seen this in other clues).
'as'+'well'+'as'='aswellas'
'aswellas' is an anagram of 'SEA-WALLS'.

Can you help me to learn more?

I've seen this clue in The Telegraph.

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