Scrap of confetti flying high, iridescent ultimately (5)
I believe the answer is:
fight
'scrap' is the definition.
(I've seen this before)
'of confetti flying high iridescent ultimately' is the wordplay.
'ultimately' says to take the final letters.
The last letters of 'of confetti flying high iridescent' are 'FIGHT'.
(Other definitions for fight that I've seen before include "Bundle" , "Scrap" , "Conflict" , "Struggle; quarrel" , "Contest" .)