De or het designkleding?

The correct Dutch article is:

de designkleding

Rule Words ending in -ing: almost always de. See the rule

How to use designkleding

the designkledingde designkleding
this designkledingdeze designkleding
that designkledingdie designkleding
our designkledingonze designkleding
your designkledingjouw designkleding
every designkledingelke designkleding
which designkleding?welke designkleding?
a big designkleding / the big designkledingeen grote designkleding, de grote designkleding