Protesting vigorously (2,2,4)
I believe the answer is:
up in arms
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">protesting vigorously</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for up in arms that I've seen before include "Protesting strongly" , "Rioting" , "Protesting vigorously, in militant mood" , "Protesting vigorously, ready for fight" , "Indignant" .)