Sea journey (6)
I believe the answer is:
voyage
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sea 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 voyage that I've seen before include "Journey by air or water" , "Journey by water or through space" , "Ocean trip" , "Sea or space journey" , "Long journey by sea or air" .)