Not noticed (6)
I believe the answer is:
unseen
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not noticed</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 unseen that I've seen before include "Lurking" , "Unnoticed" , "Translation exercise" , "Concealed" , "not processed by pupils?" .)