Australasian tree (10)
I believe the answer is:
eucalyptus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">australasian 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 eucalyptus that I've seen before include "Australasian tree" , "Evergreen tree" , "Australian tree yielding gum and oil" .)