Cast aspersions on the sociability of person in Waterford (10)

I believe the answer is:

dehumanise

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'cast' is the definition.
Both the definition and answer are verbs in their base form.
Perhaps they are linked in a way I don't understand?

'aspersions on the sociability of person in waterford' is the wordplay.
I cannot really see how this works, but
'person' could be 'human' ('human' can be a synonym of 'person') and 'human' is found in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in the Irish Times and the Irish Times (Crosaire).

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