Cancel social gathering of many nations' representatives? (4)
I believe the answer is:
undo
'cancel' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for undo that I've seen before include "(4)" , "Open, a knot say" , "Unravel or ruin" , "Dissolve - ruin" , "Subvert" .)