Toilsome (9)
(Other definitions for laborious that I've seen before include "Involving hard work" , "Gruelling" , "Using much time and effort" , "Strenuous" , "pedestrian" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">toilsome</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know this)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for arduous that I've seen before include "Tough" , "Burdensome" , "Requiring hard work" , "Steep - hard" , "Requiring great effort" .)