Block up; obstruct (7)
I believe the answer is:
occlude
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">block up</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">obstruct</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for occlude that I've seen before include "Block, obstruct" , "Cod clue to shut out" , "cover" , "Cut or shut off" , "Close up, obstruct" .)