Charlie isn't hers -- changed names (9)
I believe the answer is:
christens
'names' is the definition.
(christening is a kind of naming)
'charlie isn't hers changed' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'changed' indicates anagramming the letters.
'isnt'+'hers'='isnthers'
'isnthers' with letters rearranged gives 'hristens'.
'c'+'hristens'='CHRISTENS'
(Other definitions for christens that I've seen before include "Administers baptism" , "Names" .)