Kitten jumping on older cat

Gizmo is almost 7 months old, Willow is 5 and a half. Both are fixed. Lately Gizmo has developed a habit of trying to jump on Willow at least two or three times a day. He grabs her around the body, which she doesn't like. She wriggles out of his grip and yowls and hisses. This is followed by a face off swatting session with both cats glaring and having their ears pinned back. I keep their claws trimmed, so they're not doing any real damage. It usually goes on for about thirty seconds, and then Gizmo backs off.

Otherwise it doesn't seem to be causing either of them any stress. They eat in the same room, sleep on the same couch, and sniff one another without anything beyond the occasional hiss from Willow.

So far I've just been staying out of it. Is it something I should keep an eye on, or let them work it out between themselves?

Although I would not interfere, it would help to say "hey" "stop that" or something like it to reduce that 30 seconds to 1.

I just let them be. ReeRee does this to Fiona. She has places to escape to if she feels the need. I stopped worrying when I kept seeing her teasing him to jump after her. It's play as long as they don't swat and hiss in general on a regular basis and no one is exhibiting signs of stress. IMHO.