Hardhearted, pitiless (6)
I believe the answer is:
unkind
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">hardhearted</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">pitiless</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that pitiless can be written as unkind)</span><br/ ><br/ ></span>
(Other definitions for unkind that I've seen before include "Thoughtless -- inhumane" , "Uncaring, not generous" , "Mean, pitiless" , "Cold-hearted" , "Not gentle or considerate" .)