Boot block (4)
I believe the answer is:
last
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">boot block</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for last that I've seen before include "Final; keep going" , "Survive; after all others" , "It helps cobbler" , "Form on which a shoe is made" , "It's final for the cobbler" .)