Tie the knot but untie again (5)
I believe the answer is:
unite
'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" .)