American rewrites anthem - it's a thing of loathing (8)
I believe the answer is:
anathema
'thing of loathing' is the definition.
'anathema' can be an answer for 'thing' (I have seen 'hateful thing' mean 'anathema' so perhaps 'thing' could also mean 'anathema'). I am unsure of the 'of loathing' bit.
'american rewrites anthem it's a' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'rewrites' is an anagram indicator.
'anthem' anagrammed gives 'nathem'.
'a'+'nathem'+'a'='ANATHEMA'
Can you help me to learn more?
(Other definitions for anathema that I've seen before include "person cannot stand" , "Curse - church ban" , "Religious curse" , "Person or thing that's abhorred" , "Curse; object of loathing" .)