Book; plant (6)
I believe the answer is:
annual
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">book</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(annual is a kind of book)</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 "Plant that lives and dies within one year" , "(Of plant) living for a year or less" , "Regular publication" , "Twelve-monthly" , "Happening once each year" .)