Historic city in Surrey or Kent? (4)

I believe the answer is:

york

I'm a little stuck... Click here to teach me more about this clue!

'historic city' is the definition.
'york' can be an answer for 'city' (York is a city). I'm unsure of the 'historic' bit.

'in surrey or kent?' is the wordplay.
'in' indicates the answer is hidden within the clue.
'YORK' is hidden within 'surrey or kent'.

Can you help me to learn more?

(Other definitions for york that I've seen before include "Eboracum (L)" , "Whence the marching Grand Old Duke" , "Modern Eboracum" , "National Railway Museum city" , "A place" .)

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