Note about a balance (9)
I believe the answer is:
remainder
'balance' is the definition.
(I've seen this before)
'note about a' is the wordplay.
I cannot quite understand how this works, but
'note' could be 're' and 're' is located in the answer.
'about' could be 'a' (abbreviation in Chambers) and 'a' is present in the answer.
The remaining letters 'minder' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for remainder that I've seen before include "Leftovers" , "Dispose of unsold books cheaply" , "Unsold book; rest" , "set of unsold books" , "Rest - sell off (books) cheap" .)