Chester's river (3)
I believe the answer is:
dee
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">chester's river</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 dee that I've seen before include "Aberdeenshire river" , "Welsh banker?" , "River name" , "River of Scotland" , "Aberdeen's river" .)