Decorate some cards (4)
I believe the answer is:
deck
This clue is a double definition.
'decorate' is the first definition.
(decking is a kind of decorating)
'some cards' is the second definition.
(I've seen this before)
(Other definitions for deck that I've seen before include "Pack - floor in boat" , "Ship's platform" , "Pack of playing cards on board" , "Adorn; level on ship" , "part of ship" .)