Crossword Genius

Polishing crystal chandelier is hard occasionally - with bulky ladders initially misplaced - if they go wrong: crash! (9,6)

Ross

I believe the answer is:

hydraulic brakes

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'crash' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

I don't understand how the rest of the clue works.

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I've seen this clue in The Independent.
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