Tree's anchor (4)
I believe the answer is:
root
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tree's anchor</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for root that I've seen before include "burrow" , "Rummage for plant base" , "Source; firmly establish" , "top of tree? Hardly!" , "Turn up with the snout." .)