Very serious internal trouble? (5,3)
I believe the answer is:
civil war
'very serious internal trouble?' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe they are linked in a way I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for civil war that I've seen before include "Conflict between factions within same nation" , "Armed strife between citizens of the same country" , "Internecine strife within a country" , "Cromwell's conflict" , "power struggle" .)