Picking up waste after performing is pure tedium (5)
I believe the answer is:
ennui
'pure tedium' is the definition.
(ennui is boredom or dissatisfaction)
I don't understand the remainder of the clue.
(Other definitions for ennui that I've seen before include "Weary feeling" , "Boredom, tedium" , "Result of boredom" , "doldrums" , "Effect of boredom" .)