Defective hearing (8)
I believe the answer is:
mistrial
'defective hearing' is the definition.
(I've seen this before)
'defective hearing' is the wordplay.
'defective' becomes 'mis' (I can't justify this - if you can you should give a lot more credence to this answer).
'hearing' becomes 'trial' (as in a court case).
'mis'+'trial'='MISTRIAL'
Can you help me to learn more?
(Other definitions for mistrial that I've seen before include "Court procedure made void by error" , "When it's declared, the case must be heard again" , "legal process going wrong" , "Court hearing invalidated by error" , "Invalid court procedure" .)