Marsupial's trip wants vessel (4)
I believe the answer is:
joey
This clue might be a double definition.
'marsupial's trip' is the first definition.
The definition suggests a singular noun which matches the answer.
'vessel' is the second definition.
Both the answer and definition are singular nouns.
Maybe you can see a link between them that I don't see?
'wants' is the link.
Can you help me to learn more?
(Other definitions for joey that I've seen before include "jumper, in a pocket?" , "Sydney's youngster" , "Baby boomer's" , "Threepenny bit" , "Young kangaroo" .)