Slow boat contrary to expectation returned (3)
I believe the answer is:
tub
'slow boat' is the definition.
(tub can mean a rudimentary boat)
'contrary to expectation returned' is the wordplay.
'contrary to expectation' becomes 'but' ('but...' can mean 'contrary to expectation').
'returned' shows that the letters should be reversed in order.
'but' written backwards gives 'TUB'.
(Other definitions for tub that I've seen before include "Carton" , "Large open container" , "Slow boat; box of ice-cream" , "Container, usually for washing" , "Open container, for liquid say" .)