Thorny tree (6)
I believe the answer is:
acacia
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">thorny tree</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 acacia that I've seen before include "Plant like wattle" , "Flowering shrub of the pea family" , "Spiny tree of warm climates" , "Australian tree" , "Wattle genus" .)