Criminal vice: need testimony (8)
I believe the answer is:
evidence
'testimony' is the definition.
(testimony is evidence given in court)
'criminal vice need' is the wordplay.
'criminal' indicates an anagram.
'vice'+'need'='viceneed'
'viceneed' with letters rearranged gives 'EVIDENCE'.
(Other definitions for evidence that I've seen before include "Data" , "material presented in court" , "Matters of fact put to a court" , "Facts on which to establish verdict" , "Supporting facts" .)