I’m returning bet in error (7)
I believe the answer is:
mistake
'error' is the definition.
('mistake' can be a synonym of 'error')
'i'm returning bet' is the wordplay.
'returning' shows that the letters should be reversed in order.
'bet' becomes 'stake' (staking is a kind of betting).
'im' written backwards gives 'mi'.
'mi'+'stake'='MISTAKE'
'in' is the link.
(Other definitions for mistake that I've seen before include "Error" , "Oversight" , "Slip" , "Wrong action or judgment" , "Fault" .)