It will contain a fire (8)
I believe the answer is:
asbestos
This clue might be a double definition.
'it will contain' is the first definition.
The definition suggests a singular noun which matches the answer.
'a fire' is the second definition.
The definition and answer can be both substances as well as being singular nouns.
Perhaps there's a link between them I don't understand?
Can you help me to learn more?
(Other definitions for asbestos that I've seen before include "Fibrous mineral, used as an insulator, now deemed harmful" , "Fireproof material, now known to be dangerous" , "'Fireproof substance, dangerous to health (8)'" , "you can't inflame this" , "condemned building material" .)