Erratic cops' raid goes wrong (8)
I believe the answer is:
sporadic
'erratic' is the definition.
(thesaurus)
'cops' raid goes wrong' is the wordplay.
'goes wrong' is an anagram indicator.
'cops'+'raid'='copsraid'
'copsraid' is an anagram of 'SPORADIC'.
(Other definitions for sporadic that I've seen before include "Scattered - irregular" , "Occurring infrequently" , "Having separate patches" , "Occurring irregularly" , "Occasional - intermittent" .)