Fats Waller altered natural features (10)

I believe the answer is:

waterfalls

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'natural features' is the definition.
Although both the answer and definition are plural nouns, I can't see how they can define each other.

'fats waller altered' is the wordplay.
'altered' indicates an anagram.
'fats'+'waller'='fatswaller'
'fatswaller' anagrammed gives 'WATERFALLS'.

Can you help me to learn more?

(Other definitions for waterfalls that I've seen before include "Cataracts" , "Up north, forces" .)

I've seen this clue in The Everyman puzzle in The Observer.

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