In general, one so melancholy being solitary (8)
I believe the answer is:
lonesome
'solitary' is the definition.
('lonesome' can be a synonym of 'solitary')
'in general one so melancholy' is the wordplay.
'in' says the answer is hidden in the clue.
'LONESOME' is hidden within 'general one so melancholy'.
'being' is the link.
(Other definitions for lonesome that I've seen before include "Trail of the - Pine (Laurel and Hardy in Way Out West)" , "Abandoned" , "Dejected by lack of companions" , "Solitary (mainly US)" , "Solitary and sad" .)