Knowledge of issue besetting game (9)
I believe the answer is:
erudition
'knowledge' is the definition.
(being erudite is being learned or knowledgeable)
'issue besetting game' is the wordplay.
'issue' becomes 'edition' (edition is a kind of issue).
'besetting' indicates putting letters inside.
'game' becomes 'ru' (rugby union).
'edition' going around 'ru' is 'ERUDITION'.
'of' is the link.
(Other definitions for erudition that I've seen before include "Learnedness, scholarship" , "Great knowledge" , "Great learning" , "profound scholarly knowledge" , "Learning, scholarship" .)