Knock a vessel (5)
I believe the answer is:
barge
This clue could be a double definition.
'knock' is the first definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'a vessel' is the second definition.
(I know that barge is a type of vessel)
Can you help me to learn more?
(Other definitions for barge that I've seen before include "Move roughly; boat" , "Freight-carrying boat" , "Bump" , "Possibly lighter" , "Roughly push one's way" .)