Accountant and team regularly search vault (8)
I believe the answer is:
catacomb
'vault' is the definition.
(I have seen 'underground vault' mean 'catacomb' so perhaps 'vault' could also mean 'catacomb')
'accountant and team regularly search' is the wordplay.
'accountant' becomes 'ca' (abbreviation for chartered accountant).
'and' says to put letters next to each other.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'search' becomes 'comb' (combing is a kind of searching).
The alternating letters of 'team' are 'ta'.
'ca'+'ta'+'comb'='CATACOMB'
(Other definitions for catacomb that I've seen before include "tunnel for burial" , "Underground network" , "Professional kneader" , "Underground burial chamber" , "cellar" .)