Christmas delay heading west in vessel (7)
I believe the answer is:
galleon
'vessel' is the definition.
(type of ship)
'christmas delay heading west' is the wordplay.
'christmas' becomes 'Noel' (Noel can mean Christmas).
'delay' becomes 'lag' (lag is a kind of delay).
'heading west' says the letters should be written in reverse.
'noel'+'lag'='noellag'
'noellag' reversed gives 'GALLEON'.
'in' is the link.
(Other definitions for galleon that I've seen before include "Large Spanish sailing ship of yore" , "Old Spanish ship" , "One might sink" , "Large old sailing vessel" , "Trader" .)