Long walk or journey (4)
I believe the answer is:
trek
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">long walk</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">journey</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that journey is a is a kind of of trek)</span><br/ ><br/ ></span>
(Other definitions for trek that I've seen before include "A long arduous journey as in S Africa" , "Expedition or difficult trip" , "Long walk in the mountains?" , "A long hard march" , "Slog" .)