Peace-keepers object, arresting family regardless (10)
I believe the answer is:
unthinking
'regardless' is the definition.
(thesaurus)
'peace-keepers object arresting family' is the wordplay.
'peace keepers' becomes 'un' (I've seen this in other clues).
'object' becomes 'thing' (an object is a thing or item).
'arresting' means one lot of letters goes inside another.
'family' becomes 'kin' (synonyms).
'thing' going around 'kin' is 'thinking'.
'un'+'thinking'='UNTHINKING'
(Other definitions for unthinking that I've seen before include "Knee-jerk" , "inconsiderate" .)