Lethargy produced by boredom - or port (6)

I believe the answer is:

torpor

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'lethargy' is the definition.
(I've seen this before)

'by boredom or port' is the wordplay.
'or port' anagrams to 'TORPOR'.
But, I am not sure how the anagram is indicated.

'produced' is the link.

Can you help me to learn more?

(Other definitions for torpor that I've seen before include "State of drowsiness or languor" , "lack of energy" , "Apathetic state" , "State of complete inactivity" , "State of sluggish somnolence" .)

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

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