Calmed rumours that Thurber's antihero is under house arrest (9)

I believe the answer is:

mitigated

'calmed' is the definition.
Although both the answer and definition are past participle verbs, I can't see how one could define the other.

'rumours that thurber's antihero is under house arrest' is the wordplay.
'rumours that' indicates a 'sounds like' (homophone) clue (as in hearing a rumour).
'thurber's antihero' becomes 'Mitty' (James Thurber created the character Walter Mitty).
'is under house arrest' becomes 'gated' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'mitty' is a homophone of 'miti'.
'miti'+'gated'='MITIGATED'

I've seen this clue in The Independent.

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