All-time low (5)
I believe the answer is:
nadir
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">all-time low</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for nadir that I've seen before include "Drain into the lowest point (5)" , "Point opposite the zenith" , "Floor of drain in need of repair" , "Low spot" , "pits" .)