The writer's upset about one's ill-tempered state (8)
I believe the answer is:
missouri
'state' is the definition.
(I know that Missouri is a state)
'the writer's upset about one's ill-tempered' is the wordplay.
'the writer's upset' becomes 'mi' (I am not sure about this - if you are sure you should believe this answer much more).
'about' means one lot of letters goes inside another.
'one's' becomes 'i's' (Roman numeral).
'ill-tempered' becomes 'sour' (I've seen this in another clue).
'is'+'sour'='issour'
'mi' going around 'issour' is 'MISSOURI'.
Can you help me to learn more?
(Other definitions for missouri that I've seen before include "Flower" , "Biggest tributary of the Mississippi" , "American state, capital Jefferson City" , "So is rum I alter to the state" , "American state's" .)