Glass-half-full attitude (8)
I believe the answer is:
optimism
'glass-half-full attitude' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for optimism that I've seen before include "The tendency to always expect the best" , "Hopeful nature" , "Glass half-full attitude" , "Looking on the bright side" , "Feeling that all is going to turn out well" .)