Using last of inherited money, break the bank (4)
I believe the answer is:
dyke
'bank' is the definition.
'using last of inherited money break the' is the wordplay.
'using last of' indicates one should take the final letters.
The last letters of 'inherited money break the' are 'DYKE'.
(Other definitions for dyke that I've seen before include "Defensive earthwork" , "defensive wall" , "Barrier to prevent flooding" , "Barrier against water" , "Flood embankment" .)