Sunny day warmed up around middle of afternoon (12)

I believe the answer is:

lighthearted

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'sunny day warmed up around middle of afternoon' is the definition.
I can't judge whether this defines the answer.

'sunny day warmed up around middle of afternoon' is the wordplay.
'sunny day' becomes 'light' (I've seen this in other clues. I am not sure about the 'sunny' bit.).
'warmed up' becomes 'heated' (I've seen this before).
'around' indicates putting letters inside.
'middle of' says to take the centre.
The central letter of 'afternoon' is 'r'.
'heated' going around 'r' is 'hearted'.
'light'+'hearted'='LIGHTHEARTED'

Can you help me to learn more?

(Another definition for lighthearted that I've seen is " Cheerful".)

I've seen this clue in The Guardian.

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