Hard work — work hard (4)
I believe the answer is:
toil
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">hard work</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">work hard</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(to toil is to do strenuous work)</span><br/ ><br/ ></span>
(Other definitions for toil that I've seen before include "Work incessantly" , "Work hard and long" , "Drudgery" , "Hard physical work" , "Manual labour" .)