Dressing-up

“But since then I’ve remembered what the young gentlemen”—John and Lawrence were still the “young gentlemen” to Dorcas—“call the ‘dressing-up box.’ It’s up in the front attic, sir. A great chest, full of old clothes and fancy dresses, and what not.”

Source: wiktionary

It is a very good idea to have a large box of discarded clothes and brightly coloured pieces of material handy during Christmas for the youngsters to use for "dressing-up."

Source: wiktionary

The dressing-up in corsets, mesh-stockings and frilly aprons which has become a hallmark of Rocky Horror productions quite transformed the tasteful grey atmosphere of the Canberra Theatre[.]

Source: wiktionary