Calculating a pudding mixture (6,2)

I believe the answer is:

adding up

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'calculating' is the definition.
The answer and definition can be both to do with communicating as well as being present participle verbs.
Perhaps you can see an association between them that I don't see?

'a pudding mixture' is the wordplay.
'mixture' is an anagram indicator.
'pudding' anagrammed gives 'ddingup'.
'a'+'ddingup'='ADDING UP'

Can you help me to learn more?

(Another definition for adding up that I've seen is " Making sense of".)

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

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