Notion, thought (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">notion</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(both can mean a thought)</span><br/ ><br/ >'<span class="explanation-format__original">thought</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(idea is a kind of thought)</span><br/ ><br/ ></span>
(Other definitions for idea that I've seen before include "Plan" , "Product of the mind" , "Fancy" , "Flash of inspiration?" , "Light bulb above head" .)