Sudden game point after a bye (6)
I believe the answer is:
abrupt
'sudden' is the definition.
(similar in meaning)
'game point after a bye' is the wordplay.
'game' becomes 'RU' (rugby union).
'point' becomes 'pt' (abbreviation for point).
'after' means one lot of letters go next to another.
'bye' becomes 'b'.
'ru'+'pt'='rupt'
'a'+'b'='ab'
'rupt' put after 'ab' is 'ABRUPT'.
(Other definitions for abrupt that I've seen before include "Short in manner" , "Terse and sudden" , "Rough and quick" , "Short and rude" , "Sudden - blunt" .)