Deepest point (5)
I believe the answer is:
nadir
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">deepest point</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 "Dinar (anag.)" , "lowest of the low" , "Lower one cannot get!" , "Low spot" , "All-time low" .)