Sniper or drunk took a captive (8)
I believe the answer is:
prisoner
'captive' is the definition.
(I know that captive can be written as prisoner)
'sniper or drunk' is the wordplay.
'drunk' is an anagram indicator.
'sniper'+'or'='sniperor'
'sniperor' with letters rearranged gives 'PRISONER'.
'took a' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for prisoner that I've seen before include "Captive, incarcerated criminal" , "Incarcerated person" , "Captive or criminal in jail" , "'Convict, detainee (8)'" , "One in gaol" .)