Notes motorway going around America is top class (5)
I believe the answer is:
music
'notes' is the definition.
(a piece of music is made up of musical notes)
'motorway going around america is top class' is the wordplay.
'motorway' becomes 'MI' (resembles Mu, English motorway).
'going around' indicates putting letters inside.
'america' becomes 'us' (United States).
'is top' suggests taking the first letters.
The initial letter of 'class' is 'c'.
'mi' going around 'us' is 'musi'.
'musi'+'c'='MUSIC'
(Other definitions for music that I've seen before include "Composer's product" , "Sonic art" , "(Pleasant) sequence of sounds" , "Audible art form ..." , "Art of instrumental performance" .)