Unparalleled (6)
I believe the answer is:
unique
'unparalleled' is the definition.
(I know that unparalleled can be written as unique)
This is the entire clue.
(Other definitions for unique that I've seen before include "Singular, without equal" , "Single" , "Sole" , "Radically distinctive and without equal" , "Without equal, unparalleled" .)