Notion, in Nice (4)
I believe the answer is:
idee
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">notion in nice</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 idee that I've seen before include "could it be fixed?" , "The thought of Descartes" .)