Apish (6)
I believe the answer is:
stupid
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">apish</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for stupid that I've seen before include "Idiot" , "Barmy" , "Lacking wit or intelligence" , "Lacking in common sense" , "Dim" .)