Vague impression (6)
I believe the answer is:
notion
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vague impression</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for notion that I've seen before include "Whim or fancy" , "Concept, belief" , "An idea or casual thought" , "Vague understanding" , "Vague impression" .)