Was in debt (4)
I believe the answer is:
owed
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">was in debt</span>' is the definition.<br/ ><span class="explanation-format__explanation">('they owed' means 'they were in debt')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for owed that I've seen before include "Had an obligation to pay" , "(Sum) due for payment" , "Had a duty to pay" , "to be paid" , "Was obliged to pay" .)