American's stupid slander about singer (4-3)

'american's stupid' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'slander about singer' is the wordplay.
'slander' becomes 'mud' (as in to drag someone's name through the mud).
'about' says the letters should be written backwards.
'singer' becomes 'bass' (bass is a kind of singer).
'mud' reversed gives 'dum'.
'dum'+'bass'='DUMB-ASS'

Can you help me to learn more?