Crossword Genius

Comes out of bathroom with dirty instrument (4,4)

Ross

I believe the answer is:

soil pipe

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

'comes out of bathroom' is the definition.
I can't judge whether this definition defines the answer.

'dirty instrument' is the wordplay.
'dirty' becomes 'soil' (synonyms).
'instrument' becomes 'pipe' (pipe is a kind of instrument).
'soil'+'pipe'='SOIL-PIPE'

'with' acts as a link.

Can you help me to learn more?

I've seen this clue in The Irish Times.
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