Incoherent (12)
I believe the answer is:
inarticulate
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">incoherent</span>' is the definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for inarticulate that I've seen before include "Tongue-tied" , "Unintelligible" , "incapable of clear speech" , "Not able to speak coherently" , "incoherent" .)