Great month to introduce a star! (9)
I believe the answer is:
supernova
'star' is the definition.
(I know that supernova is a type of star)
'great month to introduce a' is the wordplay.
I cannot quite understand how this works, but
'great' could be 'super' (both can mean excellent) and 'super' is present in the answer.
'month' could be 'nov' (abbreviation for November) and 'nov' is found within the answer.
'a' is within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for supernova that I've seen before include "Exploding star that becomes much brighter" , "Star in decline" , "The sort of star" , "it puts an end to a starry career" , "Star that explodes and becomes extremely luminous" .)