Sinus specialist, for short (3)
I believe the answer is:
ent
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sinus specialist for short</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ent that I've seen before include "Tolkien tree-man" , "Tolkien's Treebeard, for one" .)