Saintly Irish woman taking odd characters from Vietnam (3)

I believe the answer is:

ita

I'm a little stuck... Click here to teach me more about this clue!

'vietnam' is the definition.
Both the answer and definition are singular nouns.
Perhaps they are linked in a way I don't understand?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for ita that I've seen before include "Palm" , "Exotic tree" , "SECOND PART OF 23" .)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app