Gentleman (3)
I believe the answer is:
sir
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">gentleman</span>' is the definition.<br/ ><span class="explanation-format__explanation">(a man may be addressed as sir)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sir that I've seen before include "Polite or formal address to male" , "Baronet's title" , "Polite form of address to a man" , "Noble title of undesirable kind" , "Form of address for a knight" .)