Burden, responsibility (4)
I believe the answer is:
onus
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">burden</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that burden can be written as onus)</span><br/ ><br/ >'<span class="explanation-format__original">responsibility</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(onus is a duty or responsibility)</span><br/ ><br/ ></span>
(Other definitions for onus that I've seen before include "Duty or responsibility" , "Responsibilty" , "albatross?" , "Encumbrance" , "Capulet opponent (R&J)" .)