Impractically idealistic (8)
I believe the answer is:
quixotic
'impractically idealistic' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for quixotic that I've seen before include "Unrealistic and impractical" , "Visionary" , "Chivalrous and romantic like Cervantes' Don" , "Extravagantly chivalrous like Cerantes' Don" , "Impracticably optimistic" .)