Half-hearted (13)
I believe the answer is:
lackadaisical
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">half-hearted</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 lackadaisical that I've seen before include "Wanting enthusiasm" , "Listless" , "Dreamily idle" , "Carelessly lazy" , "Lacking drive and rigour" .)