It depends on the recipe for the icing/frosting/glaze!
I don’t think a buttercream frosting (the kind where the main ingredients are butter and sugar, sometimes thickened with egg) would thin out well to make a glaze. I should think the glaze would be kind of greasy.
Ganaches are frequently used as frostings, fillings and glazes - and also chocolate truffle candies. A ganache is basically chocolate and cream, sometimes with a bit of butter and/or corn syrup and/or flavoring added. The “classic” proportion for ganache is 1 oz. of chocolate to 1 fluid oz. (2 Tablespons) of heavy cream, but they can quite easily be made thicker or thinner by adjusting the proportions of cream to chocolate.
So if your recipe is a ganache, it should work just fine! Thin the frosting with a bit of cream, and make sure the glaze is not so cold that it solidifies. (Having a pan of cold water and another of warm water on hand is very helpful when dealing with frostings, icings and glazes. Good for adjusting the temperature.)
There are lots of other sorts of recipes out there too. I’m just a beginning cake baker, and so far I have only made buttercream and ganache. Let us know what the recipe is, and I’m sure someone will have experience with it!