Young performer shaking rattles (7)
I believe the answer is:
starlet
'young performer' is the definition.
'starlet' can be an answer for 'performer' (starlet is a kind of performer). I'm not sure about the 'young' bit.
'shaking rattles' is the wordplay.
'shaking' is an anagram indicator.
'rattles' anagrammed gives 'STARLET'.
Can you help me to learn more?
(Other definitions for starlet that I've seen before include "young celebrity" , "Promising young film actress" , "Young film actress with a future?" .)