Vessel for the Sunday joint (4)
I believe the answer is:
ship
'vessel' is the definition.
(ship is a kind of vessel)
'the sunday joint' is the wordplay.
'the sunday' becomes 's'.
'joint' becomes 'hip' (hip is a kind of joint**).
's'+'hip'='SHIP'
'for' is the link.
(Other definitions for ship that I've seen before include "eg QE2" , "Large sailing vessel" , "Convey (goods); a vessel" , "See 18" , "Navigable vessel" .)