Long to see American partner (6)
I believe the answer is:
missus
'partner' is the definition.
(I know that missus is a type of wife)
'long to see american' is the wordplay.
'long to see' becomes 'miss' (I've seen this in another clue).
'american' becomes 'US' (abbreviation for United States).
'miss'+'us'='MISSUS'
(Other definitions for missus that I've seen before include "Wife (informal)" , "As partner" , "Wife (colloquial)" , "Dutch American" , "The old lady" .)