Additionally morose? (4,2)

I believe the answer is:

more so

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'additionally morose?' is the definition.
I can't tell whether this definition defines the answer.

'additionally morose?' is the wordplay.
'morose' anagrams to 'MORE SO'.
Though, I'm unsure how the anagram is indicated.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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