Simply not cunning by a cause of trouble (3)

I believe the answer is:

imp

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'a cause of trouble' is the definition.
I can't judge whether this definition defines the answer.

'simply not cunning' is the wordplay.
'not' indicates named letters should be taken away.
'cunning' becomes 'sly' (synonyms).
'simply' with 'sly' removed is 'IMP'.

'by' is the link.

Can you help me to learn more?

(Other definitions for imp that I've seen before include "A little devil of mischief" , "Emperor" , "Mischievous creature" , "Rascal" , "one likely to cause trouble" .)

I've seen this clue in The Globe and Mail.

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