Arduous journey (4)
I believe the answer is:
trek
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">arduous journey</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for trek that I've seen before include "Long hike" , "Long hard journey on foot" , "A long arduous walk" , "Long walk in the mountains?" , "Long and difficult trip" .)