Los Angeles police operation impossible to forget (7)

I believe the answer is:

lasting

I'm a little stuck... Click here to teach me more about this clue!

'impossible to forget' is the definition.
I can't judge whether this definition defines the answer.

'los angeles police operation' is the wordplay.
'los angeles' becomes 'LA' (abbreviation).
'police operation' becomes 'sting' (sting can mean a police operation).
'la'+'sting'='LASTING'

Can you help me to learn more?

(Other definitions for lasting that I've seen before include "Evergreen" , "long-term" , "Persistent" , "Abiding, durable" , "Enduring" .)

I've seen this clue in The Times.

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