Kind to bag excellent 50? That's more than is expected of me! (9)
I believe the answer is:
tailender
'more than is expected of me' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'kind to bag excellent 50?' is the wordplay.
'kind' becomes 'tender' (tender can mean kind or thoughtful).
'to bag' means one lot of letters goes inside another.
'excellent' becomes 'ai' (resembles 'At', old-fashioned term for excellent).
'e0?' becomes 'l' (Roman numeral).
'ai'+'l'='ail'
'tender' going around 'ail' is 'TAILENDER'.
'that's' is the link.
(Other definitions for tailender that I've seen before include "Rabbit" , "one of the last to come in" .)