Fishy sanctuary for a lot of Americans? (3,4)
I believe the answer is:
car park
'a lot of americans?' is the definition.
(Americans call a car park a parking lot)
'fishy sanctuary' is the wordplay.
'fishy' becomes 'carp' (type of fish).
'sanctuary' becomes 'ark' (I've seen this in another clue).
'carp'+'ark'='CAR PARK'
'for' acts as a link.
(Other definitions for car park that I've seen before include "designated area" , "multistorey, for example - with 27d" , "Multi-storey building with bays" , "of which many stories might be told" , "Area for transport (in which one goes into space)" .)