Not yet mature (6)
I believe the answer is:
unripe
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not yet mature</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for unripe that I've seen before include "Immature" , "Still green?" , "Not yet mature" , "Punier (anag.)" , "Not ready for picking" .)