I'm chattier performing sums? (10)

I believe the answer is:

arithmetic

'sums?' is the definition.

'i'm chattier performing' is the wordplay.
'performing' indicates an anagram.
'im'+'chattier'='imchattier'
'imchattier' anagrammed gives 'ARITHMETIC'.

(Other definitions for arithmetic that I've seen before include "kind of mean" , "Branch of mathematics" , "Calculating" , "Calculation" , "manipulation of figures" .)

I've seen this clue in The Independent.

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