Expecting power in control (8)
I believe the answer is:
pregnant
'expecting' is the definition.
(expecting can mean expecting a child)
'power in control' is the wordplay.
'power' becomes 'p'.
'in control' becomes 'regnant' (eg a queen regnant is a queen who rules).
'p'+'regnant'='PREGNANT'
(Other definitions for pregnant that I've seen before include "With child, enceinte" , "Carrying offspring in the womb" , "Expecting a baby" , "loaded" , "Expecting a child" .)