A group; in general, American (5)
I believe the answer is:
genus
'a group' is the definition.
(genus is a kind of group)
'general american' is the wordplay.
'general' becomes 'gen'.
'american' becomes 'us' (abbreviation for United States).
'gen'+'us'='GENUS'
'in' acts as a link.
(Other definitions for genus that I've seen before include "Latin class?" , "Division of family" , "Type" , "Kind or sort of" , "The Homo of Homo sapiens?" .)