Where one goes from bank to bank to get a bit of dosh (4)
I believe the answer is:
ford
'where one goes from bank to bank' is the definition.
(river crossing)
'to get a bit of dosh' is the wordplay.
'to get' becomes 'for' (as in 'to go shopping for presents'**).
'a bit of' says to take the initial letters.
The initial letter of 'dosh' is 'd'.
'for'+'d'='FORD'
(Other definitions for ford that I've seen before include "Shallow place for river crossing" , "Car firm" , "Ex-president" , "River or stream crossing" , "38th US president, Gerald" .)