Somehow agree about good music (6)
I believe the answer is:
reggae
'music' is the definition.
(I know that reggae is a type of popular music)
'somehow agree about good' is the wordplay.
'somehow' indicates an anagram.
'about' is an insertion indicator.
'good' becomes 'g' (abbreviation).
'agree' anagrammed gives 'regae'.
'regae' going around 'g' is 'REGGAE'.
(Other definitions for reggae that I've seen before include "Jamaican musical style" , "Bob Marley music" , "A Caribbean music style" , "Style of music originating in West Indies" , "Popular music of the West Indies" .)