Irish turning up to celebrate their 1916 event? (6)
I believe the answer is:
rising
'1916 event?' is the definition.
I can't judge whether this definition defines the answer.
'irish turning up to celebrate' is the wordplay.
'irish' becomes 'IR' (abbreviation).
'turning up' is a reversal indicator.
'to celebrate' becomes 'sing' (I've seen this before).
'ir' reversed gives 'ri'.
'ri'+'sing'='RISING'
'their' acts as a link.
(Other definitions for rising that I've seen before include "A revolt; getting up" , "Revolt; increasing" , "Ascending" , "Mutiny" , "Sloping up; rebellion" .)