Less than right (5)
I believe the answer is:
acute
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">less than right</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for acute that I've seen before include "Shrewd; serious" , "Critical: shrewd" , "Critical, serious" , "quick on the uptake" , "Extremely sharp or intense" .)