The remaining six balls are not required (4,4)
I believe the answer is:
left over
'the remaining' is the definition.
(I've seen this before)
'six balls are not required' is the wordplay.
I cannot really understand how this works, but
'balls' could be 'over' (I've seen this in other clues) and 'over' is located in the answer.
The remaining letters 'left' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for left over that I've seen before include "Not used up" , "Spare, remaining" , "Surplus" .)