Calm mediator turned overly emotional (12)

I believe the answer is:

melodramatic

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'overly emotional' is the definition.
I can't tell whether this defines the answer.

'calm mediator turned' is the wordplay.
'turned' indicates anagramming the letters.
'calm'+'mediator'='calmmediator'
'calmmediator' is an anagram of 'MELODRAMATIC'.

Can you help me to learn more?

(Other definitions for melodramatic that I've seen before include "Sensational" , "Exaggerated - over-emotional" , "Emotionally overblown (in theatre)" , "like ham?" .)

I've seen this clue in the Sydney Morning Herald.

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