Crossword Genius

Tie the knot but untie again (5)

Ross

I believe the answer is:

unite

I'm a little stuck... Click here to teach me more about this clue!

'tie the knot' is the definition.
(I've seen this in another clue)

'untie again' is the wordplay.
'untie' can be anagrammed to 'UNITE'.
However, I am unsure how this is indicated.

'but' acts as a link.

Can you help me to learn more?

(Other definitions for unite that I've seen before include "Bring together, become one" , "Club together" , "Combine - join" , "Put together" , "Connect" .)

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