One in the know (7)
I believe the answer is:
insider
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">one in the know</span>' is the definition.<br/ ><span class="explanation-format__explanation">(someone with inside information)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for insider that I've seen before include "member of favoured group?" , "Doing time, right, for this" , "Wrong sort of trading" , "One with privileged info" , "One 24 [IN-SECT], perhaps" .)