Answer request for help to acquire highest quality insulating material (8)
I believe the answer is:
asbestos
'insulating material' is the definition.
(material formerly used as insulation)
'answer request for help to acquire highest quality' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'request for help' becomes 'sos' (I've seen this in another clue).
'to acquire' means one lot of letters goes inside another.
'highest quality' becomes 'best' (I've seen this in another clue).
'sos' enclosing 'best' is 'sbestos'.
'a'+'sbestos'='ASBESTOS'
(Other definitions for asbestos that I've seen before include "Insulating mineral" , "Fibrous mineral, used as an insulator, now deemed harmful" , "Survivor of heat" , "Fireproof material, dangerous to health" , "Fire-resistant material, a danger to health" .)