Brainwave (5,4)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">brainwave</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 idea that I've seen before include "Clue" , "Theory" , "Thought, belief" , "Something imagined in the mind" , "Notion, belief" .)