Leap over underground chamber (5)
I believe the answer is:
vault
This clue is a triple definition!
'leap' is the first definition.
(I know that vault is a more specific form of the action leap)
'over' is the second definition.
(thesaurus)
'underground chamber' is the third definition.
(I've seen this in another clue)
(Other definitions for vault that I've seen before include "bound?" , "Bank's strongroom" , "Underground chamber - leap" , "Leap - arched ceiling" , "Cellar; leap" .)