Gap; room (5)
I believe the answer is:
space
I believe this clue is a double definition.
'gap' is the first definition.
(I've seen this in another clue)
'room' is the second definition.
(I've seen this before)
(Other definitions for space that I've seen before include ""The final frontier"" , "Blank" , "A particular area for paces" , "sci-fi theme" , "Empty area, may be outer" .)