Chuck is not the brash type (3)
I believe the answer is:
shy
'chuck' is the definition.
(both can mean to throw)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for shy that I've seen before include "Retiring; fling" , "Nervous with others" , "Throw in self-conscious way" , "guarded" , "Tongue-tied" .)