Idealistic reformer (7)
I believe the answer is:
utopian
'idealistic reformer' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for utopian that I've seen before include "Impractically idealistic" , "ideal but unrealistic" , "Perfectionist reformer" , "Of an ideal existence" , "Ideal; imaginary" .)