Visionary site laid out (8)
I believe the answer is:
idealist
'visionary' is the definition.
(idealist is a kind of visionary)
'site laid out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'site'+'laid'='sitelaid'
'sitelaid' is an anagram of 'IDEALIST'.
(Other definitions for idealist that I've seen before include "One sees things as they should be rather than how they are" , "Hopeful type" , "One pursuing perfection" , "Person with lofty and unselfish aspirations" , "Visionary" .)