Boa perhaps meeting wicked gangster (8)
I believe the answer is:
scarface
'gangster' is the definition.
(nickname of Al Capone)
'boa perhaps meeting wicked' is the wordplay.
'boa perhaps' becomes 'scarf' (boa is a kind of scarf).
'meeting' means one lot of letters go next to another.
'wicked' becomes 'ace' (ace can informally mean very good).
'scarf'+'ace'='SCARFACE'
(Other definitions for scarface that I've seen before include "Al Capone, or Tony Montana - 'Say hello to my little friend'." , "Film starring Al Pacino" , "So-called gangster" , "US gangster" , "Al Capone's nickname" .)