Just the emperor to break links with the States (7)

I believe the answer is:

severus

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'just the emperor' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'break links with the states' is the wordplay.
'break links with' becomes 'sever' (I can't justify this - if you can you should give a lot more credence to this answer).
'the states' becomes 'US' (abbreviation for the United States).
'sever'+'us'='SEVERUS'

'to' is the link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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