Group of musicians runs into singer not allowed in audition (5,4)
I believe the answer is:
brass band
'group of musicians' is the definition.
(musicians playing brass instruments)
'runs into singer not allowed in audition' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'into' means one lot of letters goes inside another.
'singer' becomes 'bass' (bass is a kind of singer).
'not allowed' becomes 'banned'.
'in audition' shows a homophone (sound like) (audition can mean hearing).
'banned' sounds like 'band'.
'r' put into 'bass' is 'brass'.
'brass'+'band'='BRASS BAND'
(Other definitions for brass band that I've seen before include "Group with trumpets etc" , "Group of wind instruments" , "Musical group" , "Group of musicians, maybe military" , "cheap alternative to gold ring" .)