Foreign banker puts a lot of money on old computer (7)
I believe the answer is:
potomac
'foreign banker' is the definition.
(US river, something with 'banks')
'a lot of money on old computer' is the wordplay.
'a lot of money' becomes 'pot'.
'on' means one lot of letters go next to another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'computer' becomes 'mac' (I've seen this before).
'pot'+'o'+'mac'='POTOMAC'
'puts' is the link.
(Other definitions for potomac that I've seen before include "Capital outflow" , "Flower" , "Water flowing" , "River of Washington DC" , "to which banks in Washington have access" .)