Stop or start playing billiards (5,3)
I believe the answer is:
break off
'stop' is the definition.
(I know that stop can be written as break off)
'start playing billiards' is the wordplay.
I cannot quite see how this works, but
'start' could be 'off' (I've seen this before) and 'off' is located in the answer.
The remaining letters 'break' 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).
'or' is the link.
Can you help me to learn more?
(Another definition for break off that I've seen is " Abruptly end (a thing)".)