Draw a veil over old America, very unpleasant (7)
I believe the answer is:
hideous
'very unpleasant' is the definition.
(hideous means horrible or unpleasant)
'draw a veil over old america' is the wordplay.
'draw a veil over' becomes 'hide' (to draw a veil over something is to obscure it).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'america' becomes 'US' (United States).
'hide'+'o'+'us'='HIDEOUS'
(Other definitions for hideous that I've seen before include "revolting" , "Extremely unpleasant" , "Horrible" , "Ghastly" , "Unsightly" .)