If they don't go out much then they often don't wear down their claws as they would naturally, so clipping off the very tips can be helpful.
My cat has one in particular that grows inwards if it's not clipped occasionally. She also struggles sliding around on slippy floors when they're very long, and often gets herself stuck hanging off the sofa or similar, which risks damaging her joints.
I'd ask the vet about it next time you go as they will be able to have a look to see if your particular cat actually needs it done, and will also be able to show you exactly how to do it and how much to cut off.
I think my vets charge £12 for clipping them all, which is worth it to me because my cat really needs it done and I'm not able to do it myself. But you may well find you can easily do it yourself, especially if your cat is fairly co-operative and there is more than one large human in the house so one can hold the cat while the other clips
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