Crossword Genius

One upset about verse is completing stanzas (6)

Ross

I believe the answer is:

envois

'completing stanzas' is the definition.
(envoi can mean the final stanza of a poem)

'one upset about verse is' is the wordplay.
'upset' shows that the letters should be reversed in order.
'about' is an insertion indicator.
'verse' becomes 'v'.
'one' back-to-front is 'eno'.
'eno' enclosing 'v' is 'envo'.
'envo'+'is'='ENVOIS'

I've seen this clue in The Guardian.
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