Danger, alack! Dog involved in mysterious activity (5-3-6)

I believe the answer is:

cloak-and-dagger

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'danger alack dog involved in mysterious activity' is the definition.
I can't judge whether this defines the answer.

'danger alack dog involved in' is the wordplay.
'involved in' indicates an anagram (involved can mean complex or confusing).
'danger'+'alack'+'dog'='dangeralackdog'
'dangeralackdog' is an anagram of 'CLOAK-AND-DAGGER'.

Can you help me to learn more?

(Other definitions for cloak-and-dagger that I've seen before include "Involving intrigue and secrecy" , "Concerned with intrigue and espionage" , "underground" .)

I've seen this clue in the Sydney Morning Herald.

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