Alumnus (3,3)
I believe the answer is:
old boy
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">alumnus</span>' is the definition.<br/ ><span class="explanation-format__explanation">(old boy is a kind of alumnus)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for old boy that I've seen before include "Former pupil - kind of network" , "Male former pupil" , "Mate" , "Male ex-pupil" , "my dear chap!" .)