Enormity of single action in the American heart (8)
I believe the answer is:
ugliness
'american heart' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Maybe there's a link between them I don't understand?
'enormity of single action in' is the wordplay.
'enormity of' becomes 'us' (I can't explain this - if you can you should believe this answer much more).
'action' is an anagram indicator.
'in' indicates putting letters inside.
'single' is an anagram of 'glines'.
'us' going around 'glines' is 'UGLINESS'.
'the' acts as a link.
Can you help me to learn more?
(Other definitions for ugliness that I've seen before include "Complete absence of beauty" , "threatening behaviour" , "Unattractive quality" , "Unattractiveness" , "Quality that gives no pleasure to the senses" .)