Uncaring behind bars admitting criminal charge (13)
I believe the answer is:
inconsiderate
'uncaring' is the definition.
(similar in meaning)
'behind bars admitting criminal charge' is the wordplay.
'behind bars' becomes 'inside' (inside can mean in prison).
'admitting' indicates putting letters inside (admit can mean to welcome in or accept).
'criminal' becomes 'con' (abbreviation for 'convict').
'charge' becomes 'rate' (rate is a kind of charge).
'inside' enclosing 'con' is 'inconside'.
'inconside'+'rate'='INCONSIDERATE'
(Other definitions for inconsiderate that I've seen before include "Thoughtless, rash" , "Careless" , "Lacking regard for the feelings of others" , "Uncaring" , "Unkind" .)