Decorates sets of cards (5)
I believe the answer is:
decks
This clue is a double definition.
'decorates' is the first definition.
(decking is a kind of decorating)
'sets of cards' is the second definition.
(I've seen this before)
(Other definitions for decks that I've seen before include "Platforms on a vessel" , "Packs of playing cards" , "Embellishes" , "Packs of cards (US)" , "Floors" .)