Went off track artist included in cover of dance song from down under (8)

'went off track' is the definition.
'derailed' can be an answer for 'went' (derailing is a kind of going). I am unsure of the 'off track' bit.

'artist included in cover of dance song from down under' is the wordplay.
'artist' becomes 'RA' (Royal Academician, member of Royal Academy of Arts).
'included in' means one lot of letters goes inside another.
'cover of' says to hollow out the word (remove centre letters) (only the letters which cover the word).
'song' becomes 'lied' (type of German song).
'from down under' shows that the letters should be reversed in order (in a down clue, letters written from bottom to top).
'dance' with its centre removed is 'de'.
'de'+'lied'='delied'
'delied' written backwards gives 'deiled'.
'ra' placed inside 'deiled' is 'DERAILED'.

Can you help me to learn more?