Limit interval - it allows long game to finish (8)
I believe the answer is:
tiebreak
'it allows long game to finish' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'limit interval' is the wordplay.
'limit' becomes 'tie' (tying is a kind of limiting).
'interval' becomes 'break' (break is a kind of interval).
'tie'+'break'='TIEBREAK'
Can you help me to learn more?
(Other definitions for tiebreak that I've seen before include "Means of deciding winner after level scores" , "Game decider" , "Tennis set decider" , "Means of settling tennis set" , "Match decider" .)