Robbery by British convict (4)
I believe the answer is:
blag
'robbery' is the definition.
(I have seen 'violent robbery' mean 'blag' so perhaps 'robbery' could also mean 'blag')
'by british convict' is the wordplay.
'by' says to put letters next to each other.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'convict' becomes 'lag' (I've seen this before).
'b' put next to 'lag' is 'BLAG'.
(Other definitions for blag that I've seen before include "Steal - wheedle" , "Scrounge - steal" , "Somehow obtain" , "Violent robbery - lying to get something" , "Get something for free by lying" .)