Piggy bank opening (4)
I believe the answer is:
slot
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">piggy bank opening</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 slot that I've seen before include "Lots (anag.)" , "This gaming machine operates by insertion of coin" , "Scheduled time - hierarchical position" , "Hole for money" , "Narrow opening, for cash say" .)