Not o'er (5)
I believe the answer is:
neath
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not o'er</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for neath that I've seen before include "Town NE of Swansea" , "Under (poetic)" , "Under, poetically" , "Welsh industrial town" , "River" .)