Careless mistake (7)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">careless mistake</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 blunder that I've seen before include "Clumsy error" , "Clumsy mistake, gaffe" , "A stupid 1 down" , "Embarrassing mistake" , "Careless mistake" .)
(Other definitions for slip-up that I've seen before include "Minor inadvertent mistake" , "Minor lapse" , "Small error" , "Mistake, blunder" .)