Confidential assistant (4)
I believe the answer is:
aide
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">confidential assistant</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for aide that I've seen before include "Officer's assistant" , "Political assistant" , "Personal assistant in the military" , "Military officer acting as assistant" , "Idea (anag)" .)