Behold old royal following flipping star (4)
I believe the answer is:
idol
'star' is the definition.
(idol is a kind of star)
'behold old royal following flipping' is the wordplay.
'behold' becomes 'lo' (archaic exclamation meaning 'look!').
'old royal' becomes 'Di' (Princess Diana).
'following' means one lot of letters go next to another.
'flipping' says the letters should be written in reverse.
'lo'+'di'='lodi'
'lodi' back-to-front is 'IDOL'.
(Other definitions for idol that I've seen before include "pop star" , "Someone much loved" , "A matinee -- is a handsome actor" , "One much admired" , "Figure worshipped - sounds like someone in 7 8" .)