Unattractive quality of American adopting single lunatic (8)
I believe the answer is:
ugliness
'unattractive quality' is the definition.
(I've seen this before)
'american adopting single lunatic' is the wordplay.
'american' becomes 'us'.
'adopting' indicates putting letters inside.
'lunatic' indicates anagramming the letters.
'single' is an anagram of 'glines'.
'us' going around 'glines' is 'UGLINESS'.
'of' acts as a link.
(Other definitions for ugliness that I've seen before include "Unsightly appearance" , "Characteristic of a duckling" , "Complete lack of beauty" , "Unsightly quality" , "Unattractiveness" .)