Four 1st level PCs fall into a pit. One of them is magically possessed (i.e. such as with a Crown of Madness) and begins attacking the other party members.
Ideally, the party would like to restrain the PC without damaging them so that when they escape they have enough hit points to survive the rest of the dungeon.
In real life, we might use a headlock or some other restraining moves like one sees commonly in wrestling matches. (Our emergency department security team regularly restrained aggressive or psychotic patients with one person taking the head and thorax and others each taking a limb.)
But there seems to be few moves that restrict actions in 5e like we would see in wrestling commonly. Grappling still allows a PC to attack or cast spells. Use the Shove action to push someone Prone and they still can attack or cast spells.
In the absence of ropes, manacles, or magic - what can first level PCs do to restrain a possessed character without damaging them significantly? Is there anything in-game that matches what we see in wrestling matches today?
(To clarify: By "restrain", we mean the layperson definition as in “to prevent from attacking” (like in wrestling) and otherwise restrict their actions - not the in-game "Restrained" condition, which still allows attacking and casting spells.)