Making a mistake (6)
I believe the answer is:
erring
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">making a mistake</span>' is the definition.<br/ ><span class="explanation-format__explanation">('err' can be a synonym of 'make a mistake')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for erring that I've seen before include "Going wrong" , "taking wrong direction" , "Sinful" , "Being incorrect" , "Making a mistake" .)