Cities laid out on a utopian scale (10)
I believe the answer is:
idealistic
'on a utopian scale' is the definition.
I can't judge whether this definition defines the answer.
'cities laid out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'cities'+'laid'='citieslaid'
'citieslaid' is an anagram of 'IDEALISTIC'.
Can you help me to learn more?
(Other definitions for idealistic that I've seen before include "High-minded - italicised (anag)" , "Striving for perfection" , "Impracticable" , "Naively impractical" , "Visionary" .)