Difficult journey (4)
(Other definitions for slog that I've seen before include "Very tiring work" , "Hit out without style" , "Work doggedly" , "Hit hard - hard work" , "Work (or walk) involving great effort" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">difficult journey</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for trek that I've seen before include "Long walk in the mountains?" , "Slog" , "Footslog" , "Expedition or difficult trip" , "A long arduous journey as in S Africa" .)