Bitterly regretting (5)
I believe the answer is:
ruing
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bitterly regretting</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ruing that I've seen before include "Feeling sorry for" , "Feeling bad" , "full of remorse?" , "Bitterly regretting" , "Regretful" .)