Ball game played to the letter (5)
I believe the answer is:
omega
'letter' is the definition.
(omega is a kind of letter of the alphabet)
'ball game played' is the wordplay.
'ball' becomes 'o' (O looks like a ball).
'played' indicates anagramming the letters (letters playing around).
'game' is an anagram of 'mega'.
'o'+'mega'='OMEGA'
'to the' is the link.
(Other definitions for omega that I've seen before include "Consummation" , "Final outcome" , "symbol of resistance?" , "Conclusion" , "24th Greek letter" .)