American beauty’s partner (6)
I believe the answer is:
missus
'partner' is the definition.
(missus is a kind of partner)
'american beauty's' is the wordplay.
I cannot really see how this works, but
'american' could be 'us' (abbreviation for United States) and 'us' is found in the answer.
The remaining letters 'miss' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for missus that I've seen before include "As partner" , "trouble and strife" , "Dutch American" , "Wife (colloquial)" , "The old lady" .)