Study of plants (6)
I believe the answer is:
botany
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">study of plants</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 botany that I've seen before include "Unlucky, doomed" , "nature study" , "13 across study" , "plants growing in one area" , "The scientific study of plants" .)