Treasury staff will lead event (4,5)
I believe the answer is:
pole vault
'event' is the definition.
(pole vault is a kind of event)
'treasury staff will lead' is the wordplay.
'treasury' becomes 'vault' (both can mean a repository).
'staff' becomes 'pole' (I've seen this before).
'will lead' says to put letters next to each other.
'vault' after 'pole' is 'POLE-VAULT'.
(Other definitions for pole vault that I've seen before include "Sergey Bubka was world champion at this event" , "Olympic field event" , "Athletic event" , "Field event -- value plot (anag)" , "High-flying Olympic event" .)