You have to say check time the PM’s in power? (5)
I believe the answer is:
reign
'power?' is the definition.
(reign can mean time in power)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for reign that I've seen before include "Rule as king or queen" , "Be champion" , "Period during which someone is dominant" , "Dominion" , "Govern" .)