Less colourful Missouri city (7)
I believe the answer is:
palermo
'city' is the definition.
(Palermo is an example)
'less colourful missouri' is the wordplay.
'less colourful' becomes 'paler' (I've seen this before).
'missouri' becomes 'mo' (abbreviation for the US state).
'paler'+'mo'='PALERMO'
(Other definitions for palermo that I've seen before include "Chief city of Sicily" , "Sicilian city" , "Italian capital" , "ity of Italy" , "Italian city" .)