Sweet song in a state (8)

I believe the answer is:

carolina

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

'state' is the definition.
(I've seen this before)

'sweet song in a' is the wordplay.
'sweet song' becomes 'carol' (carol is a kind of song. I am not sure about the 'sweet' bit.).
'carol'+'in'+'a'='CAROLINA'

Can you help me to learn more?

(Other definitions for carolina that I've seen before include "It's north and south in southern US" , "former colony" , "A clarion call for American state" , "North and South US states" , "Girl" .)

I've seen this clue in the Sydney Morning Herald.

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