Disguised stars bristle internally at musician (9)
I believe the answer is:
guitarist
'musician' is the definition.
(I know that guitarist is a type of musician)
'disguised stars bristle internally' is the wordplay.
'disguised stars' becomes 'guitar' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'internally' says to take the centre.
The centre of 'bristle' is 'ist'.
'guitar'+'ist'='GUITARIST'
'at' is the link.
Can you help me to learn more?
(Other definitions for guitarist that I've seen before include "Axeman" , "John Williams or Andres Segovia, say" , "String player" , "Eg, Django Reinhardt" , "Musician" .)