Delay or block the progress of (6)
I believe the answer is:
impede
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">delay</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >'<span class="explanation-format__original">block the progress of</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for impede that I've seen before include "Bar" , "Hold back" , "Delay, be an obstacle" , "Handicap" , "Hinder, be obstructive" .)