Taken away when you slip into the red (7)
I believe the answer is:
removed
'taken away' is the definition.
('remove' can be a synonym of 'take away')
'you slip into the red' is the wordplay.
'you slip' becomes 'move' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'into' is an insertion indicator.
'move' inserted into 'red' is 'REMOVED'.
'when' is the link.
Can you help me to learn more?
(Other definitions for removed that I've seen before include "Took away" , "Got rid of" , "Withdrawn" , "Having made a withdrawal" , "Taken away" .)