River flowing through York (4)
I believe the answer is:
ouse
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">river flowing through york</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 ouse that I've seen before include "York's river" , "One of several rivers" , "River that joins the Trent to form the Humber" , "bird has lost its tail" , "River flowing through York" .)