Bad girl admitting crime, finally banned (7)
I believe the answer is:
illegal
'banned' is the definition.
(similar in meaning)
'bad girl admitting crime finally' is the wordplay.
'bad' becomes 'ill' (associated in meaning).
'girl' becomes 'gal' (synonyms).
'admitting' indicates putting letters inside (admit can mean to welcome in or accept).
'crime finally' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'ill'+'gal'='illgal'
'illgal' going around 'e' is 'ILLEGAL'.
Can you help me to learn more?
(Other definitions for illegal that I've seen before include "Unauthorised" , "Black" , "Not in conformity with law" , "Forbidden" , "Ignoring certain acts" .)