Crossword Genius

On the throne, expecting to lose head (7)

Ross

I believe the answer is:

regnant

Here is my best explanation:

'on the throne' is the definition.
(thesaurus)

'expecting to lose head' is the wordplay.
'expecting' becomes 'pregnant' (I've seen this before).
'to lose head' means to remove the first letter.
'pregnant' with its initial letter taken off is 'REGNANT'.

This clue was last seen in The Telegraph