Shanghai sailor on channel (6)
I believe the answer is:
abduct
'shanghai' is the definition.
(thesaurus)
'sailor on channel' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'on' says to put letters next to each other.
'channel' becomes 'duct' ('duct' can be a synonym of 'channel').
'ab'+'duct'='ABDUCT'
(Other definitions for abduct that I've seen before include "Remove by force" , "Snatch away" , "Take (someone) illegally" , "Carry off illegally" , "Kidnap, make off with" .)