Day before (3)
I believe the answer is:
eve
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">day before</span>' is the definition.<br/ ><span class="explanation-format__explanation">(the eve of something is the night before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for eve that I've seen before include "The night before a festival" , "See 13 Across" , "Day before Christmas" , "Night before an event" , "Girl" .)