Rig a suit out with the first musician (9)
I believe the answer is:
guitarist
'musician' is the definition.
(I know that guitarist is a type of musician)
'rig a suit out with the first' is the wordplay.
'out with' indicates anagramming the letters (out can mean wrong or inaccurate).
'first' says to take the initial letters.
The initial letter of 'the' is 't'.
'rig'+'a'+'suit'='rigasuit'
'rigasuit' mixed up with 't' gives 'GUITARIST'.
(Other definitions for guitarist that I've seen before include "John Williams or Andres Segovia, say" , "String player" , "Player of a fretted instrument" , "Player of a particular stringed instrument" , "Axeman" .)