De or het showkleding?

The correct Dutch article is:

de showkleding

Rule Words ending in -ing: almost always de. See the rule
Meaning (Dutch) (kleding) kleding die specifiek is ontworpen of gedragen wordt om op te vallen, een personage neer te zetten of een visueel spektakel te bieden tijdens optredens, shows of presentaties.

How to use showkleding

the showkledingde showkleding
this showkledingdeze showkleding
that showkledingdie showkleding
our showkledingonze showkleding
your showkledingjouw showkleding
every showkledingelke showkleding
which showkleding?welke showkleding?
a big showkleding / the big showkledingeen grote showkleding, de grote showkleding

Meaning, plural, diminutive, pronunciation and translations: WikiWoordenboek (Dutch Wiktionary) (CC BY-SA 4.0). Example sentences: Tatoeba (CC BY 2.0 FR).