Ruling in play, originally overturned (5)
I believe the answer is:
royal
'ruling' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'in play originally overturned' is the wordplay.
'in' indicates a hidden word.
'overturned' shows that the letters should be reversed in order.
'layor' is hidden within 'play originally'.
'layor' back-to-front is 'ROYAL'.
Can you help me to learn more?
(Other definitions for royal that I've seen before include "Splendid!" , "Kingly or queenly" , "measure of paper" , "As kings and queens" , "Relating to king/queen" .)