主催（しゅさい）： sponsorship (i.e. conducting under one’s auspices); promotion; organizing; hosting; staging

主： already covered here.

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催： give (a dinner); hold (a meeting); sponsor

on-reading サイ. kun-reading もよおす.

催す（もよおす）： 1. to hold (a meeting); to give (a dinner); to show signs of 2. to feel (sensation, emotion, etc)