It means the party (Fest) of the class/course (Kurs) he or she is in. So he/she needs to buy food etc. for the party his class is having. (That is assuming the text is about someone enrolled in some kind of class; it's hard to answer those questions without context).

In diesem Kontext: Kurs = Klasse, Schule, Lehrgang, Unterricht Fest = Party, Fete Also sozusagen ein Schulfest, eine Klassenparty.