Impractical person (8)
I believe the answer is:
idealist
'impractical person' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for idealist that I've seen before include "An optimist or romantic" , "One who aspires to perfect standards" , "One who aims for perfection, may be unrealistic" , "One who pursues the perfect" , "philosopher" .)