California city police operation, memorable (7)
I believe the answer is:
lasting
'memorable' is the definition.
'california city police operation' is the wordplay.
'california city' becomes 'LA' (Los Angeles).
'police operation' becomes 'sting' (I've seen this in another clue).
'la'+'sting'='LASTING'
(Other definitions for lasting that I've seen before include "Evergreen" , "Abiding, durable" , "Permanent" , "Persistent" , "there for long while" .)