Debtor's note (3)
I believe the answer is:
iou
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">debtor's note</span>' is the definition.<br/ ><span class="explanation-format__explanation">(note of a debtor to be paid)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for iou that I've seen before include "Debt acknowledgment" , "Admission of liability" , "Proof of debt" , "Note acknowledging debt" , "Debtor's note" .)