They travel on airships and on canals (8)
I believe the answer is:
gondolas
'on canals' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps you can see a link between them that I don't see?
'they travel on airships' is the wordplay.
I cannot quite see how this works, but
'travel' could be 'do' (doing is a kind of travelling) and 'do' is found in the answer.
'on' is present in the answer.
This explanation may well be incorrect...
'and' is the link.
Can you help me to learn more?
(Other definitions for gondolas that I've seen before include "Traditional boats of Venice" , "Venetian flat-bottomed boats" .)