Expecting page on ruling (8)
I believe the answer is:
pregnant
'expecting' is the definition.
(thesaurus)
'page on ruling' is the wordplay.
'page' becomes 'p'.
'on' means one lot of letters go next to another.
'ruling' becomes 'regnant' ('regnant' can be a synonym of 'ruling').
'p'+'regnant'='PREGNANT'
(Other definitions for pregnant that I've seen before include "Expecting a child" , "Gravid" , "With child, enceinte" , "Expecting a baby" , "Carrying offspring in the womb" .)