Cassette broken may set a precedent (4,4)

I believe the answer is:

test case

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'a precedent' is the definition.
(I've seen this before)

'cassette broken' is the wordplay.
'broken' is an anagram indicator.
'cassette' anagrammed gives 'TEST-CASE'.

'may set' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.

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(Other definitions for test case that I've seen before include "Defining moment in law" , "Legal action serving as a precedent" , "Legal action where the outcome sets a precedent" , "One may set a precedent" , "Lawsuit seeking decision asprecedent" .)

I've seen this clue in The Globe and Mail.

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