Leaving money in account not collected? (3,7)
I believe the answer is:
off balance
'not collected?' is the definition.
(unstable or uncollected)
'leaving money in account' is the wordplay.
'leaving' becomes 'off' ('I'm off' means 'I'm leaving').
'money in account' becomes 'balance' (as in a bank balance).
'off'+'balance'='OFF BALANCE'
(Other definitions for off balance that I've seen before include "Not prepared" , "unprepared" .)