Lowest of the low
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lowest of the low</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 worst that I've seen before include "Direst" , "Beat" , "Most badly" , "Strangely, best" , "the pits" .)
(Other definitions for bass that I've seen before include "Fish - low voice" , "Fish for the low-voiced" , "Deep-voiced male singer" , "A fish, or the lowest pitch in music" , "Type of fish" .)
(Other definitions for rockbottom that I've seen before include "Sinking so low" , "lowest level" .)