Having used it yesterday, Clash is definitely in a weird spot when it comes to splat zones. On one hand, having a defined and confined area to fight over helps it to excel and it can keep people away decently well, but the poor turfing ability means you really need to rely on your teammates keeping the ground clean or enemies stupidly dying in the middle of the zone in order for you to strictly maintain control. One of my rounds yesterday I got a triple kill that effectively wiped the team, but since none of my teammates were around at the time doing who-knows-what, I only just barely got the zone claimed in our name before all the enemies were right back. I'd only really recommend it for maps with particularly small zones, since for as well as I did with it on Musselforge yesterday, it's a major struggle to do much unless your team cleans up and takes control early.
...Come to think of it, that makes me wonder if opening gambit might be somewhat useful. The mobility boost to get to mid quickly and take an early lead is kind of crucial for that weapon in particular.