The boat train! (4)
I believe the answer is:
wake
This clue might be a double definition.
'the boat' is the first definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'train' is the second definition.
(thesaurus)
Can you help me to learn more?
(Other definitions for wake that I've seen before include "Vigil held over a corpse" , "Ship's wash" , "Vigil; disturbed water" , "Rouse" , "Traditional Irish tribute to corpse before burial, lots of toasts" .)