Hike; arduous journey (4)
I believe the answer is:
trek
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">hike</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(trekking is a kind of hiking)</span><br/ ><br/ >'<span class="explanation-format__original">arduous journey</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for trek that I've seen before include "Slog" , "Footslog" , "A long arduous walk" , "A long hard march" , "Long hard journey on foot" .)