U-S-A chant reverberating at plant (8)

I believe the answer is:

acanthus

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

'plant' is the definition.
(acanthus is a kind of plant)

'u-s-a chant reverberating' is the wordplay.
'u-s-a chant' anagrams to 'ACANTHUS'.
However, I am not sure how this is indicated.

'at' acts as a link.

Can you help me to learn more?

(Other definitions for acanthus that I've seen before include "Ridicule" , "Widely grown Mediterranean plant with spiny leaves" , "Prickly-leaved shrub" , "Cash, aunt, for this plant" , "capital decoration" .)

I've seen this clue in The Hindu.

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