I'm sent back with money for betting slips (8)
I believe the answer is:
mistakes
'slips' is the definition.
('mistake' can be a synonym of 'slip')
'i'm sent back with money for' is the wordplay.
'sent back' says the letters should be written in reverse.
'with' is a charade indicator (letters next to each other).
'money for' becomes 'stakes' (I can't justify this - if you can you should give a lot more credence to this answer).
'im' written backwards gives 'mi'.
'mi'+'stakes'='MISTAKES'
'betting' acts as a link.
This may not be correct. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for mistakes that I've seen before include "Misguided or wrong acts" , "Errors" , "Blunders, slips" .)