Actor Harrison (4)
'actor harrison' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rex that I've seen before include "Oedipus - -" , "Dog's name; king" , "King (L.)" , "One in the palace" , "King (Latin); cat breed" .)
(Other definitions for noel that I've seen before include "A lone sort of Christmas" , "A lone Christmas in France" , "Sir - - Coward" , "Religious festival" , "Lone male name" .)