Demonstration in Northern Ireland leads to confrontation
I believe the answer is:
showdown
'confrontation' is the definition.
('showdown' can be a synonym of 'confrontation')
'demonstration in northern ireland leads' is the wordplay.
'demonstration' becomes 'show' (show is a kind of demonstration).
'in northern ireland leads' becomes 'down' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'show'+'down'='SHOWDOWN'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for showdown that I've seen before include "Final confrontation as in western film" , "Climactic finale" , "Face-off" , "Decisive confrontation" , "Denouement" .)