Rueful (9)
I believe the answer is:
regretful
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">rueful</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for regretful that I've seen before include "Wishing something hadn't happened" , "Feeling sorry, repentant" , "Sorry, rueful" , "Feeling guilt over something" , "penitent" .)