Like an optimistic outlook (4)
I believe the answer is:
rosy
'like an optimistic outlook' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rosy that I've seen before include "Pinkish; healthy" , "Of the future, promising like flower" , "Blooming - hopeful" , "Promising; hopeful" , "Pink; promising" .)