Festival star's powerful piece on PM (3,5)
I believe the answer is:
may queen
'festival star's powerful' is the definition.
I can't tell whether this definition defines the answer.
'piece on pm' is the wordplay.
'piece' becomes 'queen' (queen is a kind of piece).
'on' is a charade indicator (letters next to each other).
'pm' becomes 'May' (former UK prime minister Theresa May).
'queen' put after 'may' is 'MAY QUEEN'.
Can you help me to learn more?
(Other definitions for may queen that I've seen before include "festival girl" , "Maiden crowned with flowers in spring" , "Girl crowned in spring" .)