Over, on top of (5)
I believe the answer is:
above
I believe this is a double definition.
'over' is the first definition.
(I've seen this before)
'on top of' is the second definition.
(I've seen this in another clue)
(Other definitions for above that I've seen before include "On top of" , "Aloft" , "Given earlier (in text)" , "Mentioned earlier" , "At a higher level" .)