It will contain a fire (8)
I believe the answer is:
asbestos
This could 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.
Maybe they are linked in a way 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" .)