Shock arrangement that's surprising Irish party? (6)
I believe the answer is:
hairdo
'shock arrangement' is the definition.
(shock can mean large mass of hair)
'that's surprising irish party?' is the wordplay.
'that's surprising' becomes 'ha' (exclamation said when learning surprising news).
'irish' becomes 'IR' (abbreviation for Irish).
'party?' becomes 'do' (do can informally mean a party).
'ha'+'ir'+'do'='HAIRDO'
(Other definitions for hairdo that I've seen before include "Barnet" , "Say, crew cut" , "Arrangement of locks" , "Pageboy maybe" , "Possibly cut" .)