Required by etiquette (2,7)
I believe the answer is:
de rigueur
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">required by etiquette</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for de rigueur that I've seen before include "necessary" , "Proper" , "Required by strict etiquette or fashion (French)" , "Strictly" , "Required by custom or etiquette" .)