Finish church next to city (6)
I believe the answer is:
chrome
'finish' is the definition.
(I have seen 'Brilliant finish' mean 'chrome' so perhaps 'finish' could also mean 'chrome')
'church next to city' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'next to' means one lot of letters go next to another.
'city' becomes 'rome' (Rome is an example).
'ch'+'rome'='CHROME'
(Other definitions for chrome that I've seen before include "Shiny metal for plating" , "Brilliant finish" , "Metal plating - type of yellow" , "Metallic plate" , "Protective finish on motor vehicle fittings" .)