Deposit US cash transmitted externally (8)
I believe the answer is:
sediment
'deposit' is the definition.
(I know that deposit can be written as sediment)
'us cash transmitted externally' is the wordplay.
'us cash' becomes 'dime'.
'transmitted' becomes 'sent' ('send' can be a synonym of 'transmit').
'externally' is an insertion indicator (some letters go on the outside of others).
'dime' going into 'sent' is 'SEDIMENT'.
(Other definitions for sediment that I've seen before include "Matter settling (on seabed)" , "End times (anag)" , "Lees" , "Matter sinking to the bottom of a liquid" , "Stuff that settles to the bottom" .)