Ruling, and expecting to have no power (7)
I believe the answer is:
regnant
'ruling' is the definition.
(as in a queen regnant, a queen who rules by birth)
'expecting to have no power' is the wordplay.
'expecting' becomes 'pregnant' (expecting can mean expecting a child).
'to have no' suggests deleting specific letters.
'power' becomes 'p' (symbol in physics).
'pregnant' with 'p' removed is 'REGNANT'.
'and' is the link.
(Other definitions for regnant that I've seen before include "Reigning" , "(Queen) in her own right" , "Current" , "Not like a consort" , "exercising authority" .)