club activities; group activities
Refers to the organized activities of a student club or circle, typically in a university setting. Often implies a less formal or more interest-based group than a strict school club (部活).
Many students participate in club activities at university.
I made friends through club activities.
Compound of サークル (from English 'circle') and 活動 (activity). The term became common in Japanese university culture to describe extracurricular group activities.