Wise crossing America in a banger? (7)
I believe the answer is:
sausage
'a banger?' is the definition.
(banger is a kind of sausage)
'wise crossing america' is the wordplay.
'wise' becomes 'sage' ('sage' can be similar in meaning to 'wise').
'crossing' is an insertion indicator.
'america' becomes 'usa' ('U.S.A.' can be a synonym of 'america').
'sage' enclosing 'usa' is 'SAUSAGE'.
'in' acts as a link.
(Other definitions for sausage that I've seen before include "Eg, chipolata" , "Long, bagged meat product" , "BBQ food?" , "Tasty tube of meat" , "E.g. salami, bratwurst" .)