Immature, inexperienced (6)
I believe the answer is:
callow
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">immature</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">inexperienced</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for callow that I've seen before include "23 [BRIGHTONIAN] actor" , "Immature and inexperienced, like youth" , "Inexperienced or innocent" , "Immature and inexperienced, as youth often is" , "Young and inexperienced" .)