Kidnap sailor by channel (6)
I believe the answer is:
abduct
'kidnap' is the definition.
(I know that kidnap can be written as abduct)
'sailor by channel' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'by' means one lot of letters go next to another.
'channel' becomes 'duct' (duct is a kind of channel).
'ab'+'duct'='ABDUCT'
(Other definitions for abduct that I've seen before include "Hijack" , "Kidnap, carry person off by force" , "Criminally remove to an undisclosed location" , "Remove by force" , "Take (someone) away by force" .)