City's ruination (it's old-fashioned) in a painful condition (8)

I believe the answer is:

cystitis

'a painful condition' is the definition.
(medical complaint)

'city's ruination it's old-fashioned' is the wordplay.
'ruination' indicates an anagram (the letters are ruined).
'it's old-fashioned' becomes 'tis' (archaic contraction of 'it is').
'citys' is an anagram of 'cysti'.
'cysti'+'tis'='CYSTITIS'

'in' acts as a link.

I've seen this clue in The Guardian.

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