Not all auditors can add up (4)
I believe the answer is:
some
'not all' is the definition.
(I know this)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for some that I've seen before include "Hard work" , "Several" , "A little; not a little" , "Undefined number" , "An unspecified quantity, not all" .)