Claude Monet taking part in protest (4)
I believe the answer is:
demo
'protest' is the definition.
(demonstration)
'claude monet taking part' is the wordplay.
'taking part' says the answer is hidden in the clue.
'DEMO' can be found hidden inside 'claude monet'.
'in' is the link.
(Other definitions for demo that I've seen before include "In brief, a public event as of protest under dome" , "Brass instrument valve" , "March (abbr)" , "illustration" , "Protest march (sl.)" .)