Involvement in celebration cut short (4)
I believe the answer is:
part
'involvement' is the definition.
(part is a kind of involvement)
'celebration cut short' is the wordplay.
'celebration' becomes 'party' (I've seen this before).
'cut short' means to remove the last letter.
'party' with its last letter taken off is 'PART'.
'in' acts as a link.
(Other definitions for part that I've seen before include "Sever; portion" , "Piece; divide" , "unemployed actor hopes for" , "Element" , "Member" .)