Prosecute at law (3)
I believe the answer is:
sue
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">prosecute at law</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 sue that I've seen before include "Appeal" , "Take proceedings against (a person)" , "Use to take to court" , "Proceed legally against (someone)" , "Litigious girl" .)