Crossword Genius

We're in trouble over water treated chemically (2-2)

Ross

I believe the answer is:

oh-oh

I'm a little stuck... Click here to teach me more about this clue!

'water treated chemically' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'we're in trouble over' is the wordplay.
I cannot quite see how this works, but
'over' could be 'o' (cricket abbreviation) and 'o' is located in the answer.
The remaining letters 'hoh' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Independent.
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