Dismiss party protecting Northern Ireland (6)
I believe the answer is:
banish
'dismiss' is the definition.
(thesaurus)
'party protecting northern ireland' is the wordplay.
'party' becomes 'bash' (bash is a kind of party).
'protecting' indicates putting letters inside.
'northern ireland' becomes 'ni'.
'bash' enclosing 'ni' is 'BANISH'.
(Other definitions for banish that I've seen before include "outlaw" , "Exile (someone)" , "Drive away, maybe from country" , "Deport, exile" , "Expel from a community or group" .)