Saviour fee? That's offensive (7,6)

I believe the answer is:

cavalry charge

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'offensive' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'saviour fee?' is the wordplay.
'saviour' becomes 'cavalry' (I can't justify this - if you can you should give a lot more credence to this answer).
'fee?' becomes 'charge' (fee is a kind of charge).
'cavalry'+'charge'='CAVALRY CHARGE'

'that's' acts as a link.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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