Rates as a flower (5)

I believe the answer is:

aster

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

'flower' is the definition.
(type of flower)

'rates as a' is the wordplay.
'rates' anagrams to 'ASTER'.
But, I'm unsure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for aster that I've seen before include "Flower of the daisy family - rates (anag)" , "Purple pink flowered plant" , "Daisy-like plant" , "Tears (anag) - plant" , "Christmas daisy" .)

I've seen this clue in The Irish Independent.

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