Arcturus, Altair or Antares (4)
I believe the answer is:
star
I believe this clue is a double definition.
'arcturus' is the first definition.
(I've seen this in another clue)
'altair or antares' is the second definition.
(I've seen this in another clue)
(Other definitions for star that I've seen before include "Famous person" , "Famous entertainer" , "For example, Marilyn Monroe" , "Astronomer - dreamer" , "Top celebrity" .)