Impractically idealistic (8)
I believe the answer is:
quixotic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">impractically idealistic</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)