Everyone is taken aback, missing one left in Spanish city (7)

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

'everyone is taken aback missing one left' is the wordplay.
'everyone' becomes 'all' (all people).
'is taken' means one lot of letters go next to another.
'aback missing' becomes 'ives' (I can't explain this - if you can you should give a lot more credence to this answer).
'one left' is a reversal indicator.
'all'+'ives'='allives'
'allives' backwards is 'SEVILLA'.

'in' is the link.

Can you help me to learn more?