The song is totally dreadful, all round (6)
I believe the answer is:
ballad
'the song' is the definition.
(ballad is a kind of song)
'totally dreadful all round' is the wordplay.
'totally' becomes 'all' (I've seen this in another clue).
'dreadful' becomes 'bad' (similar in meaning).
'all round' indicates putting letters inside.
'all' going within 'bad' is 'BALLAD'.
'is' is the link.
(Other definitions for ballad that I've seen before include "Slow sentimental song" , "Love song" , "Lay, narrative song" , "Slow romantic song" , "Form of verse" .)