Bill raised with good reason (5)
I believe the answer is:
cause
'reason' is the definition.
(I know that reason can be written as cause)
'bill raised with good' is the wordplay.
'bill' becomes 'ac' (short for account).
'raised' shows that the letters should be reversed in order (going up in a down clue).
'with' is a charade indicator (letters next to each other).
'good' becomes 'use' (in phrases like 'it's no good', 'any good?' etc).
'ac' in reverse letter order is 'ca'.
'ca'+'use'='CAUSE'
(Other definitions for cause that I've seen before include "Reason; belief" , "Make happen; something deserving support" , "Bring about" , "why some people fight" , "It brings about an effect" .)