Get a stasis rifle, and/or Seamoth zapper module. Neither helps defend the cyclops directly but they sure do help you re-educate would-be threats. (Repulsion rifle might work too, but I haven't bothered with that.):O
There are ghost leviathans down there! I'd be terrified to take the Cyclops down there, especially since unlike the Seamoth, it's not fast enough to just run away if it gets into trouble.
Most hostile enemies in the game are pretty easy to deal with if you just avoid them, but ghost leviathans, warpers, and crabsquids... those guys are jerks. I haven't yet died to any of them, but I did have a very terrifying ten minutes or so trying to explore a seabase while a crabsquid growled at me through the window, EMP'd me every ten seconds, and occasionally started attacking the Seamoth on general principle, forcing me to rush out to repair it.
In particular I've got a policy of knifing the heck out of any Warper that looks at me crosswise after tagging it with a stasis shot. And I scared one crabsquid so badly with my Seamoth that it fled into a wall and seems to have been unable to find its way back out. I haven't picked a serious fight with a ghost leviathan yet...but I'm pretty sure that's something you can reasonably aim to win if you have to.
Also note the cyclops is tough and fast. Aggressive things generally have pretty limited ranges, and if you just punch the flank speed and run through you can clear them before getting in much trouble. That's how I used to deal with boneshark swarms, back when they would attack a Cyclops. Also how I got out of my terrifying and unplanned Reaper encounter last night. Obviously you need to know where to run to, though, which can be a problem in cave systems.