Wise person imports an American banger (7)
I believe the answer is:
sausage
'banger' is the definition.
(I've seen this before)
'wise person imports an american' is the wordplay.
'wise person' becomes 'sage' (sage can mean a wise or holy person).
'imports' is an insertion indicator.
'an' becomes 'a'.
'american' becomes 'us' (abbreviation for United States).
'a'+'us'='aus'
'sage' placed around 'aus' is 'SAUSAGE'.
(Other definitions for sausage that I've seen before include "Long, bagged meat product" , "Minced meat and fat in cylindrical skin" , "Chipolata, for example" , "sort of roll?" , "that should be edible" .)