Remaining on top (4)
I believe the answer is:
over
I believe this is a double definition.
'remaining' is the first definition.
(as in 'we ate them all but had one over')
'on top' is the second definition.
(I've seen this before)
(Other definitions for over that I've seen before include "bridge?" , "Six consecutive bowls in cricket" , "See 19" , "Finished; six balls" , "Finished like bowling session" .)