Vessel that travels (fruitfully?) by road (3,3)
I believe the answer is:
jam jar
'road' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'vessel that travels fruitfully? by' is the wordplay.
'vessel' becomes 'jar' (type of container).
'that travels fruitfully?' becomes 'jam' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'by' means one lot of letters go next to another.
'jar' put after 'jam' is 'JAM JAR'.
Can you help me to learn more?
(Other definitions for jam jar that I've seen before include "Container for conserve" , "Container for preserve" .)