You can use regular melted butter, but with the milk solids it will look a little milky/whitish on the pie.
“Clarified butter is butter that has been rendered to separate the milk solids and water from the butter fat. Typically it is produced by melting butter and allowing the different components to separate by density. The water evaporates, some solids float to the surface and are skimmed off, and the remainder of the milk solids sink to the bottom and are left behind when the butter fat (which would then be on top) is poured off. The components that are not butter fat are usually discarded.”
juat use a little brush to paint the top of the pie a couple of times