Jumbos, say, had risen anew after rail transport (9)

'jumbos' is the definition.
Both the answer and definition are plural nouns.
Maybe you can see an association between them that I don't see?

'had risen anew after rail transport' is the wordplay.
I cannot really see how this works, but
an anagram of 'risen' is 'iners' which is present in the answer.
an anagram of 'rail' is 'airl' which is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

'say' acts as a link.

Can you help me to learn more?