Blazing star (4)
I believe the answer is:
nova
'blazing star' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nova that I've seen before include "Sudden light increase" , "sun" , "Faint star that suddenly flares into brightness and then fades again" , "Exploding star" , "Suddenly bright star" .)