Nautical platform (4)
I believe the answer is:
deck
'nautical platform' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for deck that I've seen before include "part of ship" , "Pack of cards (US)" , "Pack - floor in boat" , "Adorn; pack of cards" , "Adorn; level on ship" .)