Babyish (9)
I believe the answer is:
infantile
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">babyish</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for infantile that I've seen before include "in early stage of development" , "Inflate in childish way" , "for kids" , "Babyish" .)