Longed, desperately, to be prosperous (6)
I believe the answer is:
golden
'be prosperous' is the definition.
(synonyms)
'longed desperately' is the wordplay.
'desperately' indicates anagramming the letters.
'longed' is an anagram of 'GOLDEN'.
'to' is the link.
(Other definitions for golden that I've seen before include "Brilliant" , "Excellent" , "In Woodstock we are this" , "Autumnal flower" , "Gilded, pale yellow" .)