Music track about chance to set up parties (8)
I believe the answer is:
rhapsody
'music' is the definition.
(I've seen this before)
'track about chance to set up parties' is the wordplay.
'track' becomes 'RY' (abbreviation for railway).
'about' means one lot of letters goes inside another.
'chance' becomes 'hap' (archaic term for chance).
'to set up' says the letters should be written backwards.
'parties' becomes 'dos' (do is a kind of party).
'dos' written backwards gives 'sod'.
'hap'+'sod'='hapsod'
'ry' going around 'hapsod' is 'RHAPSODY'.
(Other definitions for rhapsody that I've seen before include "ecstatic words?" , "Ecstatic statement or romantic musical composition" , "'''... in Blue'' (Gershwin) (8)'" , "Shop yard (anag)" , "Irregular and emotional musical composition" .)