Potter's implement (3)
I believe the answer is:
cue
I believe this clue is a double definition.
'potter's' is the first definition.
(a cue pots balls in snooker etc)
'implement' is the second definition.
(cue is a kind of implement)
(Other definitions for cue that I've seen before include "Rod used in billiards" , "Prompting" , "Sporting rod" , "Actor's signal" , "Billiard stick - hint - signal" .)