Not warranted (5)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not warranted</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 undue that I've seen before include "Unwarranted, inordinate" , "Excessive - unwarranted" , "Improper" , "Extreme" , "Excessive, unreasonable" .)