Endlessly (2,9)
I believe the answer is:
ad infinitum
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">endlessly</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ad infinitum that I've seen before include "Indefinitely" , "Endlessly, forever (Lat.)" .)