Djokovic fails to finish stellar event (4)
I believe the answer is:
Here is my best explanation:
'stellar event' is the definition.
'djokovic fails to finish' is the wordplay.
'djokovic' becomes 'novak' (Novak Djokovic).
'fails to finish' means to remove the last letter.
'novak' with its last letter taken away is 'NOVA'.
(Other definitions for nova that I've seen before include "It shines", "Sudden light increase", "Newly bright star", "Kind of star", "Star showing a sudden temporary increase in brightness", "A star that suddenly becomes brighter for a while", "Faint star that suddenly flares into brightness and then fades again", "Star that becomes much brighter for short time", "A new flaring star" and "Exploding star".)