Beer (unknown quantity) and Spanish wine (no OJ) in old city (10)

I believe the answer is:

alexandria

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

'old city' is the definition.
'Alexandria' can be an answer for 'city' (Alexandria is an example). I'm not certain of the 'old' bit.

'beer unknown quantity and spanish wine no oj' is the wordplay.
'beer' becomes 'ale' (type of beer).
'unknown quantity' becomes 'x' (algebra).
'spanish wine' becomes 'rioja' (I've seen this before).
'no' suggests deleting specific letters.
'rioja' with 'oj' taken out is 'ria'.
'ale'+'x'+'and'+'ria'='ALEXANDRIA'

'in' is the link.

Can you help me to learn more?

(Other definitions for alexandria that I've seen before include "Egyptian Mediterranean port" , "Chief port of Egypt" , "Egyptian city" .)

I've seen this clue in The Everyman puzzle in The Observer.

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