Musician rings any number to get mother admitted (8)
I believe the answer is:
bandsman
'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' is a charade indicator (letters next to each other).
'mother' becomes 'ma' (ma can mean mother).
'admitted' is an insertion indicator (inserted letters are let in or admitted).
'bands'+'n'='bandsn'
'bandsn' enclosing 'ma' is 'BANDSMAN'.
(Another definition for bandsman that I've seen is " musician".)