Alma mater visitor (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">alma mater visitor</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 alum that I've seen before include "Name given to a specific chemical compound and a class of them" , "Compound used in tanning and dying" , "double sulphate" , "Potassium compound; IoW sandy bay" , "Sulphate used in dyeing and tanning" .)