River through Wales and England (6)
I believe the answer is:
severn
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">river through wales and england</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 severn that I've seen before include "River rising in Wales" , "Gloucester's river" , "River flowing into the Bristol Channel" , "Welsh and English river" , "UK's longest river" .)