Knot in a tree (5)
I believe the answer is:
gnarl
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">knot in a tree</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for gnarl that I've seen before include "Rough lump (on a tree)" , "Something lumpy" , "lump of wood" , "Lump, growl" , "Lump or knot in a tree" .)