Exhaustively (2,6)
I believe the answer is:
at length
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">exhaustively</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 at length that I've seen before include "Interminably" , "Finally" , "In due course" , "Fully extended" , "eventually" .)