States positively upset, losing American accent (6)
I believe the answer is:
stress
'accent' is the definition.
(stress is a kind of accent)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for stress that I've seen before include "'Worry, pressure (6)'" , "suffering" , "Particular emphasis" , "Lay emphasis on - it's a strain" , "Feeling of pressure" .)