Garment right for concealing British criminal (6)
I believe the answer is:
robber
'criminal' is the definition.
(robber is a kind of criminal)
'garment right for concealing british' is the wordplay.
'garment' becomes 'robe' (robe is a kind of garment**).
'right for' becomes 'r' (I've seen this in other clues).
'concealing' means one lot of letters goes inside another.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'robe'+'r'='rober'
'rober' going around 'b' is 'ROBBER'.
(Other definitions for robber that I've seen before include "One who steals" , "One who thieves" , "Mugger" , "Highwayman, for example" , "Burglar" .)