Kidnap sailor on canal (6)
I believe the answer is:
abduct
'kidnap' is the definition.
('abduct' can be a synonym of 'kidnap')
'sailor on canal' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'on' means one lot of letters go next to another.
'canal' becomes 'duct' ('duct' can be a synonym of 'canal').
'ab'+'duct'='ABDUCT'
(Other definitions for abduct that I've seen before include "Snatch away" , "Kidnap, shanghai" , "Kidnap, make off with" , "Take (someone) illegally" , "Remove by force" .)