Crossword Genius

Void has odd water courses (7)

Ross

I believe the answer is:

nullahs

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'water courses' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'void has odd' is the wordplay.
'void' becomes 'null' (synonyms).
'odd' indicates an anagram.
'has' with letters rearranged gives 'ahs'.
'null'+'ahs'='NULLAHS'

Can you help me to learn more?

(Another definition for nullahs that I've seen is " Drains in India".)

I've seen this clue in the Sydney Morning Herald.
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