Much attached to a game of chance (5)
I believe the answer is:
lotto
'a game of chance' is the definition.
(I've seen this before)
'much attached to' is the wordplay.
'much' becomes 'lot' (I've seen this in other clues).
'attached' is a charade indicator (letters next to each other).
'lot'+'to'='LOTTO'
(Other definitions for lotto that I've seen before include "Game like bingo" , "National game with large money prizes" , "Game of chance similar to bingo" , "Venetian painter - gambling game" , "Housey-housey, bingo" .)