"The door's open!" (5)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">the door's open</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 enter that I've seen before include "Set foot in" , "put in for a race" , "Move into" , "Enrol" , "Come/go in" .)