Born villain's dialect? (6)
I believe the answer is:
brogue
'dialect?' is the definition.
(thesaurus)
'born villain's' is the wordplay.
'born' becomes 'b'.
'villain' becomes 'rogue' (rogue is a kind of villain).
'b'+'rogue'='BROGUE'
(Other definitions for brogue that I've seen before include "Kind of shoe" , "last work?" , "Stout shoe - Irish accent" , "Irish accent or strong shoe" , "Irish or Scottish accent?" .)