Begin bidding (4)
I believe the answer is:
open
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">begin bidding</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 open that I've seen before include "Release" , "Not closed or secret" , "Overt" , "Candid or unlocked" , "Frank, candid" .)