Conceal nothing in America - that's not attractive (7)
I believe the answer is:
hideous
'not attractive' is the definition.
I can't judge whether this defines the answer.
'conceal nothing in america' is the wordplay.
'conceal' becomes 'hide' (synonyms).
'nothing' becomes 'O' (looks like zero - 0).
'in america' becomes 'U.S.' ('U.S.' is part of 'america').
'hide'+'o'+'us'='HIDEOUS'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for hideous that I've seen before include "Unsightly" , "Frightful" , "Ghastly" , "revolting" , "Extremely unpleasant" .)