Vessel capsized on duck (5)
I believe the answer is:
liner
'vessel' is the definition.
(I know that liner is a type of ocean liner)
'capsized on duck' is the wordplay.
'capsized' says the letters should be written in reverse.
'on' becomes 're' ('on' can be mean 'with reference to').
'duck' becomes 'nil' (both can mean zero).
're'+'nil'='renil'
'renil' reversed gives 'LINER'.
(Other definitions for liner that I've seen before include "eg QE2" , "bin-bag?" , "LP's inner sleeve" , "Passenger transport" , "Pleasure cruiser" .)