Tree knot (5)
(Another definition for burl that I've seen is " Small knot in wool".)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tree knot</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 gnarl that I've seen before include "Something lumpy" , "Rough lump (on a tree)" , "Lump, growl" , "lump of wood" , "Lump or knot in a tree" .)