Additionally morose maybe (4,2)

I believe the answer is:

more so

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

'morose maybe' is the wordplay.
'maybe' is an anagram indicator.
'morose' anagrammed gives 'MORE SO'.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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