Thus Nat has an article on music (6)
I believe the answer is:
sonata
'music' is the definition.
(sonata is a kind of music)
'thus nat has an article' is the wordplay.
'thus' becomes 'so' (synonyms).
'has' is a charade indicator (letters next to each other).
'an article' becomes 'a' (example of the part-of-speech).
'so'+'nat'+'a'='SONATA'
'on' is the link.
(Other definitions for sonata that I've seen before include "Type of musical composition" , "Instrumental work" , "Instrumental composition for soloist" , "Beethoven's 'Moonlight', for example" , "Piece of classical music" .)