Laboured (6)
I believe the answer is:
toiled
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">laboured</span>' is the definition.<br/ ><span class="explanation-format__explanation">('toil' can be a synonym of 'labour')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for toiled that I've seen before include "Worked incessantly" , "Struggled long and hard" , "Worked long and hard" , "Worked or laboured very hard" , "Worked laboriously and long" .)