Abandon security and barge head-down into custody (4,4)
I believe the answer is:
jump bail
'barge head-down into custody' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'abandon security' is the wordplay.
'abandon' becomes 'jump' (I can't justify this - if you can you should believe this answer much more).
'security' becomes 'bail' (I've seen this before).
'jump'+'bail'='JUMP BAIL'
'and' acts as a link.
Can you help me to learn more?
(Another definition for jump bail that I've seen is " Abscond from court appearance".)