Cocoon, lag (8)
I believe the answer is:
insulate
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">cocoon</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">lag</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for insulate that I've seen before include "Lag" , "Lean suit (anag.)" , "Thermally protect" , "Protect from heat, cold, noise etc" , "Protect (from, eg, heat)" .)