Detectives are ditching English operations, backtracking on an irregular basis (8)
I believe the answer is:
sporadic
'on an irregular basis' is the definition.
(sporadic means irregular)
'detectives are ditching english operations backtracking' is the wordplay.
'detectives' becomes 'CID' (abbreviation for Criminal Investigation Department).
'ditching' indicates named letters should be taken away.
'english' becomes 'E' (abbreviation).
'operations' becomes 'ops' (abbreviation).
'backtracking' shows that the letters should be reversed in order.
'are' with 'e' taken out is 'ar'.
'cid'+'ar'+'ops'='cidarops'
'cidarops' written backwards gives 'SPORADIC'.
(Other definitions for sporadic that I've seen before include "Occurring here and there, scattered" , "Occurring irregularly" , "Occurring now and then - cop raids (anag)" , "Occurring infrequently" , "Fitful, intermittent" .)