It's no good by all accounts (3,4)
I believe the answer is:
bad debt
'it's' is the definition.
I can't tell whether this definition defines the answer.
'no good by all accounts' is the wordplay.
'no good' becomes 'bad' (similar in meaning).
'by all accounts' becomes 'debt' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'bad'+'debt'='BAD DEBT'
Can you help me to learn more?
(Other definitions for bad debt that I've seen before include "Irredeemable liability" , "Unrecoverable sum of money owed" , "Money loaned that cannot be recovered" , "Write it off - it's uncollectible" , "Money owed but not collectible" .)