Abduct or kidnap (8)
I believe the answer is:
This clue is a double definition.
'abduct' is the first definition.
(shanghaiing is a kind of abducting)
'kidnap' is the second definition.
(shanghaiing is a kind of kidnaping)
(Other definitions for shanghai that I've seen before include "Force into service" , "Oddly, you can gain hash in the Chinese city" , "Kidnap sailors" , "once used to drug sailors, possibly" , "Dragoon" .)