Irregular police looking back over disorganised raid (8)
I believe the answer is:
sporadic
'irregular' is the definition.
(similar in meaning)
'police looking back over disorganised raid' is the wordplay.
'police' becomes 'cops' (cop can informally mean a police officer).
'looking back' says the letters should be written in reverse.
'over' is an insertion indicator.
'disorganised' indicates an anagram.
'cops' reversed gives 'spoc'.
'raid' with letters rearranged gives 'radi'.
'spoc' going around 'radi' is 'SPORADIC'.
(Other definitions for sporadic that I've seen before include "Fitful, intermittent" , "Occurring here and there, scattered" , "Isolated; intermittent" , "Happening irregularly" , "Having separate patches" .)