Unblock (5)
I believe the answer is:
clear
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unblock</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for clear that I've seen before include "Easy to see or understand" , "Understandable" , "Lucid; to empty" , "Comprehensible" , "Obvious; remove obstructions from" .)