Mediocrity, nobody (9)
I believe the answer is:
nonentity
I believe this clue is a double definition.
'mediocrity' is the first definition.
(thesaurus)
'nobody' is the second definition.
(I know that nobody can be written as nonentity)
(Other definitions for nonentity that I've seen before include "Unimportant person" , "not even second fiddle produced" , "Insignificant person" , "A nobody" , "cipher" .)