About to seize ten thousand pounds? It's in banks in America (3,6)
I believe the answer is:
rio grande
'in america' is the definition.
('Rio Grande' is part of 'america')
'about to seize ten thousand pounds? it's in' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'to seize' indicates putting letters inside.
'ten' becomes 'IO' (IO resembles r0).
'thousand pounds?' becomes 'grand' (slang).
'it's in' is an insertion indicator.
're' going around 'io' is 'rioe'.
'rioe' going around 'grand' is 'RIO GRANDE'.
'banks' is the link.
This may not be correct. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for rio grande that I've seen before include "River flowing between USA and Mexico" , "Long river" , "American flower" , "Waterway rising in Colorado" , "River boundary between the US and Mexico" .)