Singular
'singular' is the definition.
(I know that singular can be written as unique)
This is the entire clue.
(Other definitions for unique that I've seen before include "One-off" , "Singular, without equal" , "Unlike anything else" , "Alone of its kind" , "Sole" .)
'singular' is the definition.
(synonyms)
This is all the clue.
(Other definitions for only that I've seen before include "Except that; single" , "Siblingless (child)" , "Existing alone with no other, perhaps a child" , "Single, solitary" , "See 6" .)
'singular' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lone that I've seen before include "Companionless" , "He likes to operate by himself" , "Single and isolated" , "Sole" , "Solitary, sounds like advance" .)
'singular' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for solitary that I've seen before include "Confinement" , "Recluse" , "Lacking companions" , "Isolated; hermit" , "Being the only one" .)
(Another definition for onefold that I've seen is " Simple".)