Give it back and the balance is at zero again (7)
I believe the answer is:
restore
'give it back' is the definition.
I can't judge whether this defines the answer.
'the balance is at zero again' is the wordplay.
'the balance' becomes 'rest' (I've seen this before).
'is at' says to put letters next to each other.
'zero' becomes 'O' (O resembles 0).
'again' becomes 're' (prefix meaning 'again').
'rest'+'o'+'re'='RESTORE'
'and' is the link.
Can you help me to learn more?
(Other definitions for restore that I've seen before include "Give or put back" , "Refurbish" , "Repair, put back" , "Cure" , "Give back - return to former state" .)