A bit of belief in a league game (5)
I believe the answer is:
final
'game' is the definition.
(final is a type of game)
'a bit of belief in a league' is the wordplay.
'a bit of' indicates the answer is hidden within the clue (I've seen 'a bit' mean this (the answer is formed by a bit of the clue)).
'FINAL' is hidden in the letters of 'belief in a league'.
(Other definitions for final that I've seen before include "Like one's journey to cemetery" , "Not to be altered" , "The last exam or leg of competition" , "Concluding" , "Last in a series of games or contests" .)