Shy people picked to perform (4)
I believe the answer is:
cast
I believe this clue is a double definition.
'shy' is the first definition.
(both can mean to throw)
'people picked to perform' is the second definition.
(eg people cast in a play)
(Other definitions for cast that I've seen before include "Throw the actors' group" , "Allot roles in a play" , "Allocate roles" , "Form < > company" , "Play's actors" .)