Bishop in gown has line in crime (7)
I believe the answer is:
robbery
'crime' is the definition.
(robbery is a kind of crime)
'bishop in gown has line' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'in' means one lot of letters goes inside another.
'gown' becomes 'robe' ('robe' can be a synonym of 'gown'**).
'has' is a charade indicator (letters next to each other).
'line' becomes 'ry' (abbreviation for railway).
'b' placed within 'robe' is 'robbe'.
'robbe'+'ry'='ROBBERY'
'in' acts as a link.
(Other definitions for robbery that I've seen before include "Theft of property" , "Heist" , "Criminal action" , "Theft, stealing" , "Theft maybe with violence" .)