Gymnastics jump (5)
I believe the answer is:
vault
'gymnastics jump' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for vault that I've seen before include "Burial chamber - jump across" , "Spring - clear - cellar" , "Strongroom or burial chamber" , "Underground chamber - leap" , "Leap - arched ceiling" .)