Criminal's abandoned scruples and discipline (7)
I believe the answer is:
science
'discipline' is the definition.
(science is a kind of discipline)
'criminal's abandoned scruples' is the wordplay.
'criminal' becomes 'con' (abbreviation for 'convict').
'abandoned' is a deletion indicator.
'scruples' becomes 'conscience' ('conscience' can be a synonym of 'scruples').
'conscience' with 'con' taken out is 'SCIENCE'.
'and' is the link.
(Other definitions for science that I've seen before include "Organised body of knowledge" , "-- Fiction; -- park" , "Study of physical things by observation and experiment" , "Biology, perhaps?" , "M [MUSEUM]" .)