Unfilled or unfolded (4)
I believe the answer is:
open
I believe this clue is a double definition.
'unfilled' is the first definition.
(I've seen this in another clue)
'unfolded' is the second definition.
(similar in meaning)
(Other definitions for open that I've seen before include "Not secret or hidden" , "Undo; exposed to attack" , "Unrestricted; ready for business" , "ready to entertain new ideas" , "Not shut or secret" .)