Dangerous fire proofing can be found in mansions occasionally, including the finest (8)
I believe the answer is:
asbestos
'dangerous fire proofing can be found' is the definition.
I can't tell whether this definition defines the answer.
'mansions occasionally including the finest' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'including' indicates putting letters inside.
'the finest' becomes 'best' (I've seen this in another clue).
The alternating letters of 'mansions' are 'asos'.
'asos' enclosing 'best' is 'ASBESTOS'.
'in' is the link.
Can you help me to learn more?
(Other definitions for asbestos that I've seen before include "Fire defence" , "Fire-resistant material, a danger to health" , "you can't inflame this" , "dangerous dust" , "Heat-resistant fibrous mineral" .)