The magic circle spell has the following effect in its description:
The creature can't willingly enter the cylinder by nonmagical means.
So the theory is that if someone possessed by a ghost is restrained, then they can be forceably pushed into a magic circle. The ghost possessing the person cannot willingly enter and therefore must leave the body it's possessing.
This seems to make sense, but there are two possible problems with it. First, if the possessed person is forced into a magic circle, does that imply that the ghost is actually being forced into it? I guess another way of asking that is, is the barrier sufficient to force the ghost to voluntarily break possession to avoid unwillingly entering it?
Secondly, the description of the possession effect states:
The possession lasts until the body drops to 0 hit points, the ghost ends it as a bonus action, or the ghost is turned or forced out by an effect like the dispel evil and good spell.
The dispel evil and good spell is 5th level. Magic circle is 3rd level. A guideline I've always followed (although I don't know if it is in any way official) is that when an effect gives an example of a spell that could break it, an alternative spell would need to be of a similar level. The rationale is that if possession is strong enough that it requires something like a 5th level spell to force the ghost out, then the amount of power in a 3rd level spell just isn't going to do it.
Best Answer
It will work to expel the ghost
When you push the possessed creature into the magic circle, the ghost does not willingly enter the circle. You are forcing it to enter the circle.
Magic Circle does not say they cannot enter the circle at all, only, that they cannot enter it willingly. The possessed creature would be pushed into the circle.
Magic Circle says this about creatures within the Circle
This is entirely separate from other effects of the circle. Creatures within the circle cannot be possessed by a creature of the selected type. As the creature now is within the circle, and is possessed by a creature of the selected type, which it cannot be, the possession will end.
As you point out, one could construe to read "an effect like dispel evil and good" to refer to just the nature of the effect (being able to end possession), or the power and nature of the effect. This will be up to DM ruling.