Cocoon, lag (8)
I believe the answer is:
insulate
This clue is a double definition.
'cocoon' is the first definition.
(I've seen this before)
'lag' is the second definition.
(I've seen this before)
(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)" .)