A simple frock to occupy my time

The story:

I didn't know what he meant by that, but the '80s
had a lot of artsy stupid songs and I figured it was
just one of those. Or maybe he was talking about a
girl, you know, like how men call women "skirts".
Well, I thought this forever until it was on at my
ex boyfriend's house. I asked, "why does he want a
dress?" My ex was baffled. I said, " you know, the
simple frock." He looked at me like I was nuts,
laughed at me and said, "it's PROP". Well, now that
makes much more sense!