I have a website structure in which I have created a custom-taxonomy(topic). Whenever a custom-taxonomy-term is created say "1", its three verbs a,b,c are created and they have their templates of there own.

So to look it in URL form.

custom-taxonomy-term: example/topic/1

custom-taxonomy-term-verb: example/topic/1/a , example/topic/1/b & example/topic/1/c.

And if someone goes to example/topic/1 they should be automatically redirected to example/topic/1/a.

I have a diagram attached below for better understanding.

How can I get this behaviour in WordPress?

PS: I am not putting all the three in custom-taxonomy templates because of SEO reasons. I want to have an a, b & c for every custom-taxonomy term.