Game on date following a battle (9)
I believe the answer is:
agincourt
'battle' is the definition.
(Agincourt is an example)
'game on date following a' is the wordplay.
'game' becomes 'gin' (gin is a kind of game).
'on' says to put letters next to each other.
'date' becomes 'court' (I've seen this in another clue).
'following' means one lot of letters go next to another.
'gin' put next to 'court' is 'gincourt'.
'gincourt' put after 'a' is 'AGINCOURT'.
(Other definitions for agincourt that I've seen before include "English victory in 1415" , "1415 battle in the Pas-de-Calais" , "Battle in Hundred Years' War" , "where Henry met Constable" , "French village" .)