Lone, solitary (6)
I believe the answer is:
single
I believe this clue is a double definition.
'lone' is the first definition.
(synonyms)
'solitary' is the second definition.
(similar in meaning)
(Other definitions for single that I've seen before include "Individual - unmarried" , "Unattached" , "Sort of person" , "Still miss" , "Sole" .)