Be mischievous, switch the file and remain quiet (6)

I believe the answer is:

elfish

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'be mischievous' is the definition.
(synonyms)

'switch the file and remain quiet' is the wordplay.
'switch' indicates anagramming the letters.
'and' says to put letters next to each other.
'remain quiet' becomes 'sh' (I can't justify this - if you can you should give a lot more credence to this answer).
'file' with letters rearranged gives 'elfi'.
'elfi'+'sh'='ELFISH'

Can you help me to learn more?

(Other definitions for elfish that I've seen before include "Mischievous" , "Tricky" .)

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

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