Sounds like the total, but isn't (4)

I believe the answer is:

some

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'but isn't' is the definition.
I can't judge whether this definition defines the answer.

'sounds like the total' is the wordplay.
'sounds like' indicates a 'sounds like' (homophone) clue.
'the total' becomes 'sum' (synonyms).
'sum' is a homophone of 'SOME'.

Can you help me to learn more?

(Other definitions for some that I've seen before include "Part" , "An unspecified quantity, not all" , "Hard work" , "Undefined number" , "Several" .)

I've seen this clue in the Evening Standard.

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