Long journey on foot (4)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">long journey on foot</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for trek that I've seen before include "A long arduous journey as in S Africa" , "A long hard march" , "Extended journey" , "Long hard journey on foot" , "Long hike" .)
(Other definitions for hike that I've seen before include "Trek" , "Long walk - sharp increase" , "Long walk; big price rise" , "Walk for pleasure in the country" , "Increase cost" .)