Too young (8)
I believe the answer is:
underage
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">too young</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 underage that I've seen before include "one too young" , "Not old enough to exercise legal right" , "Immature" , "Not yet eligible to vote - too young" , "Need a rug (anag.)" .)