rocn n river trekking pole

I'm not familiar with that make, but a couple of general things (assuming they're similar to my Leki poles) ...

First you need to loosen the clasp and locate a small, usually plastic, wheel and turn it clockwise a little, probably only a quarter or half turn, you may need a flat head screwdriver. to do this Then try closing the clasp again, it should feel tighter. If you overdo the adjustment you won't be able to close the clasp at all, so back it off a bit until you can close it with a decent amount, but not too much pressure.

Secondly, the bottom section on most poles is tapered towards the end. If you try and fasten the clasp too low down, it won't grip enough and will give way. The best strategy is to make sure each section is of equal length, there's usually markings on the sections in cm, so just play around with them a bit, making sure each section is on the same setting, until you find the ideal length, on my Leki poles, for example, it's 125cm, but will vary depending how tall you are.

This is what the wheel looks like on mine for reference ...