River ferried by Charon (4)
I believe the answer is:
styx
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">river ferried by charon</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 styx that I've seen before include "Underworld river; sounds like remote area" , "classical stream" , "Hellish current" , "River Charon rowed on" , "River around Hades" .)