Sun hat
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sun hat</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 topi that I've seen before include "Headgear" , "Tropical sun-hat" , "Pith-helmet" , "cover in the heat" , "that goes ahead" .)