Mathematical indicator of negative balance perhaps (5,4)
I believe the answer is:
minus sign
This clue is a double definition.
'mathematical indicator' is the first definition.
(symbol for subtraction)
'negative balance perhaps' is the second definition.
(I know that subtraction symbol is a type of minus sign)
'of' acts as a link.
(Other definitions for minus sign that I've seen before include "Symbol indicating subtraction" , "Maths operator" , "indication of negativity?" , "indicating deduction!" , "Subtraction indicator" .)