Work excessively hard (5)
I believe the answer is:
slave
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">work excessively hard</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 slave that I've seen before include "Person owned by another" , "Person owned for work" , "Person who is owned by someone" , "One in bondage" , "Person who is the property of another" .)