Outsiders in Surrey wrongly took bloody beating (7)

I believe the answer is:

systole

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'bloody beating' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

'outsiders in surrey wrongly took' is the wordplay.
'outsiders in' suggests removing the centre.
'wrongly took' becomes 'stole' (stealing is a kind of taking. I am not sure about the 'wrongly' bit.).
'surrey' with its centre removed is 'sy'.
'sy'+'stole'='SYSTOLE'

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