Fully developed, grown up (6)
I believe the answer is:
mature
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">fully developed</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">grown up</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for mature that I've seen before include "reach the end of term" , "Grow older" , "Age" , "Fully grown and adult" , "Fully-developed" .)