Strange bug confused American agent (10)

I believe the answer is:

gangbuster

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

'american agent' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'strange bug confused' is the wordplay.
'confused' is an anagram indicator.
'strange'+'bug'='strangebug'
'strangebug' is an anagram of 'GANGBUSTER'.

Can you help me to learn more?

(Another definition for gangbuster that I've seen is " policeman".)

I've seen this clue in The Independent.

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