Yearly book; plant (6)
I believe the answer is:
annual
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">yearly book</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">plant</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(annual is a type of plant)</span><br/ ><br/ ></span>
(Other definitions for annual that I've seen before include "Book published yearly" , "Lasting for a year" , "Plant; yearbook" , "Reference book that's published every year" , "Type of year book" .)