Overt (4)
I believe the answer is:
open
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">overt</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that overt can be written as open)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for open that I've seen before include "Frank - ready for business" , "Exposed to the air" , "Candid and undisguised" , "Exposed; free" , "Plain" .)