Make a blunder (3)
I believe the answer is:
err
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">make a blunder</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 err that I've seen before include "Slip up" , "Deviate" , "Leave the straight and narrow" , "Miss the mark" , "Bungle" .)