US state securing border in getting crook (8)
I believe the answer is:
criminal
'crook' is the definition.
(synonyms)
'us state securing border in' is the wordplay.
'us state' becomes 'Cal' (abbreviation for California).
'securing' indicates putting letters inside.
'border' becomes 'rim' (both can mean an edge).
'rim'+'in'='rimin'
'cal' placed around 'rimin' is 'CRIMINAL'.
'getting' acts as a link.
(Other definitions for criminal that I've seen before include "Being sought by police" , "Punishable by law" , "Mafioso, possibly" , "An habitual breaker of the law" , "Deplorable, shocking" .)