It exists to tackle burning issues (4,6)
I believe the answer is:
fire engine
'it exists to tackle' is the definition.
The definition suggests a singular noun which matches the answer.
'burning issues' is the wordplay.
'burning' becomes 'fire' (fire is a kind of burning).
'issues' becomes 'engine' (I can't justify this - if you can you should give a lot more credence to this answer).
'fire'+'engine'='FIRE-ENGINE'
Can you help me to learn more?
(Other definitions for fire engine that I've seen before include "Operate ignition" , "vehicle needed in emergency" , "emergency aid" , "Red vehicle" , "Vehicle carrying a ladder and hoses" .)