Very bottom (5)
(Other definitions for floor that I've seen before include "American story" , "Lower limit" , "Storey of a building" , "Dumbfound" , "Knock down; storey" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">very bottom</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 nadir that I've seen before include "deep despair" , "worst-case scenario?" , "most unsuccessful point" , "businessman formerly escaping justice" , "pits" .)