Toy with theatrical piece suggested by slender gent on the left (9)
I believe the answer is:
plaything
'toy' is the definition.
(synonyms)
'theatrical piece suggested by slender gent on the left' is the wordplay.
I cannot quite see how this works, but
'piece' could be 'lay' (lay is a kind of piece) and 'lay' is found in the answer.
'slender' could be 'thin' (similar in meaning) and 'thin' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'with' acts as a link.
Can you help me to learn more?
(Other definitions for plaything that I've seen before include "used to impact king's conscience?" , "Toy" , "source of amusement" , "someone treated lightly" .)