Root for mother knocking back entitled man in front of musician? (5,5)

'root' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'mother knocking back entitled man in front of musician?' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'knocking back' is a reversal indicator.
'entitled man' becomes 'sir' (sir is a kind of man. I am not sure about the 'entitled' bit.).
'in front of' says to put letters next to each other (some letters go in front of others).
'musician?' becomes 'piper' (someone playing the bagpipes).
'sir' backwards is 'ris'.
'ma'+'ris'+'piper'='MARIS PIPER'

'for' acts as a link.

Can you help me to learn more?