Surplus ball on several deliveries of balls (9)
I believe the answer is:
overspill
'of balls' is the definition.
The definition suggests a singular noun which matches the answer.
'surplus ball on several deliveries' is the wordplay.
'surplus' becomes 's' (this could be a standard abbreviation I've not previously seen).
'ball' becomes 'pill' (humorous term for the ball in some sports).
'on' means one lot of letters go next to another.
'several deliveries' becomes 'over' (a cricket over consists of six deliveries).
's'+'pill'='spill'
'spill' put after 'over' is 'OVERSPILL'.
Can you help me to learn more?
(Other definitions for overspill that I've seen before include "for people moving out of slums?" , "Excess; surplus (population)" , "Surplus population moving elsewhere" , "Excess liquid" , "excessive amount" .)