Spoil, hinder (6)
I believe the answer is:
impair
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">spoil</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that spoil can be written as impair)</span><br/ ><br/ >'<span class="explanation-format__original">hinder</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for impair that I've seen before include "Spoil, degrade" , "blunt" , "Courteous man (colloq.)" , "Hurt or handicap" , "Hobble" .)