Impractical dreamer
I believe the answer is:
idealist
'impractical dreamer' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for idealist that I've seen before include "Romantic sort" , "Person with lofty and unselfish aspirations" , "One seeking perfection" , "Utopian" , "Hopeful type" .)