Hymn about America facing American abomination (8)
I believe the answer is:
anathema
'abomination' is the definition.
(thesaurus)
'hymn about america facing american' is the wordplay.
'hymn' becomes 'anthem' ('anthem' can be a synonym of 'hymn'**).
'about' indicates putting letters inside.
'america' becomes 'a' (common abbreviation - e.g. in organisation names).
'facing' says to put letters next to each other.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'anthem' enclosing 'a' is 'anathem'.
'anathem'+'a'='ANATHEMA'
(Other definitions for anathema that I've seen before include "Religious curse" , "denunciation" , "thing we detest" , "Object of detestation" , "Condemned or excommunicated by church" .)