Unsatisfactory (13)
I believe the answer is:
disappointing
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unsatisfactory</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 disappointing that I've seen before include "Not as good as one had hoped" , "Poor" , "Failing to satisfy" .)