Gambling game interrupted by a piece of music - a disordered mixture (7)
I believe the answer is:
farrago
'a disordered mixture' is the definition.
(I've seen this before)
'gambling game interrupted by a piece of music' is the wordplay.
'gambling game' becomes 'faro' (I've seen this before).
'interrupted by' indicates putting letters inside.
'a piece of music' becomes 'rag' (I've seen this before).
'faro' placed around 'rag' is 'FARRAGO'.
(Other definitions for farrago that I've seen before include "A motley hotchpotch of things" , "Jumbled mixture" , "Hash" , "Confused mixture" , "Motley assortment of things" .)