Tinny tone upset nobody (9)
I believe the answer is:
nonentity
'nobody' is the definition.
('nonentity' can be a synonym of 'nobody')
'tinny tone upset' is the wordplay.
'upset' indicates an anagram.
'tinny'+'tone'='tinnytone'
'tinnytone' with letters rearranged gives 'NONENTITY'.
(Other definitions for nonentity that I've seen before include "Insignificant person" , "not even second fiddle produced" , "No leading player" , "cipher" , "Unimportant person" .)