Power seen in sun over a cataclysmic stellar explosion (9)
I believe the answer is:
supernova
'cataclysmic stellar explosion' is the definition.
'supernova' can be an answer for 'explosion' (I have seen 'cosmic explosion' mean 'supernova' so perhaps 'explosion' could also mean 'supernova'). I'm unsure of the 'cataclysmic stellar' bit.
'power seen in sun over a' is the wordplay.
'power seen in' becomes 'su' (I can't justify this - if you can you should give a lot more credence to this answer).
'sun' becomes 'nova' (I've seen this before).
'over' means one lot of letters goes inside another.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'su'+'nova'='sunova'
'sunova' placed around 'per' is 'SUPERNOVA'.
Can you help me to learn more?
(Other definitions for supernova that I've seen before include "it puts an end to a starry career" , "Star in decline" , "The sort of star" , "Star that explodes and becomes extremely luminous" , "Exploding star that becomes much brighter" .)