Knightly address (3)
I believe the answer is:
sir
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">knightly address</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sir that I've seen before include "Knight's title" , "... ___ John Major" , "Title given to 10 Across" , "Title of 1 across" , "Title of Kt or Bart" .)