Allow to get into round: it could be for the better (8)
I believe the answer is:
roulette
'it could be for the better' is the definition.
(people bet on roulettes)
'allow to get into round' is the wordplay.
'allow to' becomes 'let' (I've seen this in another clue).
'get into' means one lot of letters goes inside another.
'round' becomes 'route' (eg a newspaper round).
'let' going within 'route' is 'ROULETTE'.
(Other definitions for roulette that I've seen before include "it's for the better, supposedly" , "Whirling numbered wheel" , "Form of gambling" , "Wheel for the gambler" , "Table game" .)