Shut in 1,000 after senior detectives go overboard, perhaps (9)
I believe the answer is:
disembark
'overboard perhaps' is the definition.
I can't judge whether this defines the answer.
'shut in 1000 after senior detectives go' is the wordplay.
'shut in d000 after senior detectives' becomes 'dis' (I am not sure about this - if you are sure you should believe this answer much more).
'go' becomes 'embark' (embarking is a kind of going).
'dis'+'embark'='DISEMBARK'
Can you help me to learn more?
(Other definitions for disembark that I've seen before include "to set oneself apart from trader, say" , "Step on dry land" , "Get off" , "Go ashore" .)