Part of a constellation (4)
I believe the answer is:
star
'part of a constellation' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for star that I've seen before include "Five-pointed celestial body" , "For example, Marilyn Monroe" , "Cult sci-fi film" , "Famous entertainer" , "Play a leading role" .)