America in song for party (8)
I believe the answer is:
carousal
'for party' is the definition.
(I've seen this before)
'america in song' is the wordplay.
'america' becomes 'usa' (synonyms).
'in' indicates putting letters inside.
'song' becomes 'carol' (carol is a kind of song).
'usa' put within 'carol' is 'CAROUSAL'.
(Other definitions for carousal that I've seen before include "Merry drinking party" , "revelry" , "Revels" , "Drunken party" , "rave" .)