Mystify (5)
I believe the answer is:
stump
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mystify</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that stump is a type of mystify)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for stump that I've seen before include "Flummox" , "Nonplus" , "What's left after cutting" , "Truncated trunk" , "Fox" .)