Flower posies arranged by coroner (9)

I believe the answer is:

coreopsis

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'flower' is the definition.
The definition and answer can be both plants as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'posies arranged by coroner' is the wordplay.
'arranged' indicates an anagram (letters rearranged).
'by' says to put letters next to each other.
'coroner' becomes 'cor' (I can't justify this - if you can you should believe this answer much more).
'posies' with letters rearranged gives 'eopsis'.
'eopsis' after 'cor' is 'COREOPSIS'.

Can you help me to learn more?

I've seen this clue in The Independent.

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