Jamesian heroine, excellent Italian, absolutely stops me (6)
I believe the answer is:
maisie
'jamesian heroine' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'excellent italian absolutely stops me' is the wordplay.
'excellent' becomes 'ai' (resembles 'As', old-fashioned term for excellent).
'italian absolutely' becomes 'si' (I can't justify this - if you can you should believe this answer much more).
'stops' means one lot of letters goes inside another (stopping can mean blocking a gap).
'ai'+'si'='aisi'
'aisi' placed inside 'me' is 'MAISIE'.
Can you help me to learn more?
(Another definition for maisie that I've seen is " James's girl".)