Damaged cassette leads to legal action (4,4)
I believe the answer is:
test case
'legal action' is the definition.
(test case is a kind of legal action)
'damaged cassette' is the wordplay.
'damaged' indicates an anagram.
'cassette' with letters rearranged gives 'TEST CASE'.
'leads to' acts as a link.
(Other definitions for test case that I've seen before include "important legal action" , "Possible legal precedent" , "Legal precedent setter" , "Precedent-setting trial" , "Precedent established" .)