Starlet cast causes disquiet (7)
I believe the answer is:
rattles
'causes disquiet' is the definition.
Although both the answer and definition are verbs in their -s form, I cannot see how they can define each other.
'starlet cast' is the wordplay.
'cast' is an anagram indicator (letters are dispersed or cast around).
'starlet' with letters rearranged gives 'RATTLES'.
Can you help me to learn more?
(Other definitions for rattles that I've seen before include "Starlet (anag)" , "Noisy toys for babies" .)