Arduous trip (4)
I believe the answer is:
trek
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">arduous trip</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for trek that I've seen before include "A long arduous march" , "Difficult journey on foot" , "Slog" , "A long arduous journey as in S Africa" , "A long arduous walk" .)