Doctor can treat surrounding area easily (2,1,6)

I believe the answer is:

at a canter

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'easily' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'doctor can treat surrounding area' is the wordplay.
'doctor' indicates an anagram.
'surrounding' is an insertion indicator.
'area' becomes 'a' (maths abbreviation).
'can'+'treat'='cantreat'
'cantreat' with letters rearranged gives 'atcanter'.
'atcanter' placed around 'a' is 'AT A CANTER'.

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I've seen this clue in The Sunday Times and The Times.

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