Duplicities lack upside of being lawful (5)

I believe the answer is:

licit

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'being lawful' is the definition.
(synonyms)

'duplicities lack upside' is the wordplay.
'LICIT' is hidden within the letters.
However, I am unsure how the hidden word is indicated.

'of' acts as a link.

Can you help me to learn more?

(Other definitions for licit that I've seen before include "Not forbidden, lawful" , "Within the law" , "Permitted by law" , "not banned" , "OK?" .)

I've seen this clue in The Irish Times.

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