There is no "club soccer" but there is a "Soccer Club" which is semi competitive against other california schools. My friends who played were gone a lot (almost every weekend sometimes), they kinda take it seriously. Besides that, there really ain't no solid intramural soccer options at UCI. If you are greek you can play in so-so greek tournaments, or you can sign up for soccer teams at the ARC but they are usually for very quick tournies or like 4-10 week leagues I remember, if you are lucky (depends on the quarter). I heard some of them are getting more enjoyable but in the past it was like overpriced and over too quick (plus you have to sign up fast and sometimes you must form your own teams... pain in the ass). Some of them are pretty laid back (mixed girl/guy teams) and some are simply indoor tournies. At least they are trying to create more options.
By my 4th/5th year at UCI I was tired of trying to figure out all the soccer options and didn't want to pay up the ass to play, so I found a bunch of random foreign students and kick back UCI students and we played pickup games at the ARC and fields near campus. I'm sure that sort of thing is still popular with all the foreign kids going to UCI these days. But get ready to rub up against hairy 45 year old grad students from Milan lmao.