Sailor approaching channel for Shanghai (6)
I believe the answer is:
abduct
'for shanghai' is the definition.
(I've seen this in another clue)
'sailor approaching channel' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'approaching' means one lot of letters go next to another.
'channel' becomes 'duct' (synonyms).
'ab'+'duct'='ABDUCT'
(Other definitions for abduct that I've seen before include "Take (someone) illegally" , "Kidnap, make off with" , "Snatch away" , "Hijack" , "Carry off illegally" .)