White dwarf, say (4)
I believe the answer is:
star
'white dwarf say' is the definition.
(white dwarf is a kind of star)
This is all the clue.
(Other definitions for star that I've seen before include "A heavenly body or film favourite" , "Red Dwarf?" , "For example, Marilyn Monroe" , "Pointed symbol" , "Famous entertainer" .)