It's a term of greeting, sunshine! (4,3)

I believe the answer is:

good day

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

'greeting sunshine' is the definition.
'good-day' can be an answer for 'greeting' (you might say 'good day' to greet someone). I'm not certain of the 'sunshine' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Another definition for good day that I've seen is " welcome".)

I've seen this clue in the Evening Standard.

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