Glazier's paste (5)
I believe the answer is:
putty
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">glazier's paste</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for putty that I've seen before include "Window fixer" , "Malleable form of glas holder" , "Whiting and linseed oil paste" , "Window-sealing paste" , "Glazier's paste" .)