A ball game played on board (9)
I believe the answer is:
bagatelle
'a ball game' is the definition.
'bagatelle' can be an answer for 'game' (bagatelle is a kind of game). I am not certain of the 'a ball' bit.
'played on board' is the wordplay.
I cannot quite understand how this works, but
'on' could be 'at' (I've seen this in other clues) and 'at' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bagatelle that I've seen before include "Trifling matter" , "Trifle - game with pins and balls" , "Trifle; pinball game" , "drop in the ocean!" , "no serious work" .)