The white in snooker (3,4)
![Ross](/clue/static/ross-mug.min.png)
'the white in snooker' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cue ball that I've seen before include "Object struck by a snooker player" , "Jimmy White's white?" , "The white in snooker" , "Feature of pub entertainment" .)
(Another definition for cueball that I've seen is " white?".)