Insulate (3)
I believe the answer is:
lag
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">insulate</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for lag that I've seen before include "Fall behind on march" , "Prisoner" , "Wrap water-pipes; fall behine" , "Convict (slang)" , "Cover pipes" .)