Score at the wrong end (3,4)
I believe the answer is:
own goal
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">score at the wrong end</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 own goal that I've seen before include "bad mistake" , "Goon law (anag.)" , "Self-inflicted wound" , "A self-inflicted injury, from soccer" , "Defender's faux pas" .)