Flaring star (4)
I believe the answer is:
nova
'flaring star' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nova that I've seen before include "Exploding star" , "Sudden light increase" , "Star that becomes much brighter for short time" , "Faint star that suddenly flares into brightness and then fades again" , "Star that ejects a cloud, thus becoming brighter" .)