Bargains to bring duck aboard ship (6)
I believe the answer is:
steals
'bargains' is the definition.
('steal' can be a synonym of 'bargain')
'duck aboard ship' is the wordplay.
'duck' becomes 'teal' (teal is a type of duck).
'aboard' means one lot of letters goes inside another.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'teal' placed inside 'ss' is 'STEALS'.
'to bring' is the link.
(Other definitions for steals that I've seen before include "Pilfer, filch" , "Takes property without right or permission" , "Robs" , "Pilfers" , "Takes without owner's consent" .)