Lac (5)
I believe the answer is:
resin
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lac</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 resin that I've seen before include "Sticky tree exudation" , "Sticky stuff from pine trees" , "Very important part of plastics industry" , "Sticky exudation from trees" , "Lac" .)