My man is in the middle of the fist fight in the club.
Remember 殴る, which means "to punch"? Well, add on 合う and you've got punches that have come together with other punches. By "come together" I mean your fist is coming in contact with someone's face, and their fist is coming in contact with your kidneys. In other words, this is a fistfight.
The readings come from 殴る and 合う, punched together.