Musician rings any number to get mother admitted (8)

'musician' is the definition.
(bandsman is a kind of musician)

'rings any number to get mother admitted' is the wordplay.
'rings' becomes 'bands' ('band' can be a synonym of 'ring').
'any number' becomes 'n' (mathematical symbol for an unspecified number).
'to get' says to put letters next to each other.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'admitted' is an insertion indicator (inserted letters get admitted).
'bands'+'n'='bandsn'
'bandsn' enclosing 'ma' is 'BANDSMAN'.