Sole; the same (3)
I believe the answer is:
one
I believe this is a double definition.
'sole' is the first definition.
(synonyms)
'the same' is the second definition.
(I've seen this in another clue)
(Other definitions for one that I've seen before include "Smallest whole number" , "A certain; single person" , "Single, sole" , "Unit" , "Figure" .)