Polite behaviour (4,7)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">polite behaviour</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 courtesy that I've seen before include "Civility, politeness" , "Polite behaviour" , "good breeding" , "Politeness and respect for others" , "Good manners" .)