The central body in the solar system scarlet-backed is separate (6)
I believe the answer is:
sunder
'is separate' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for sunder that I've seen before include "Nursed so as to tear apart" , "Break in pieces" , "Separate the odd red sun" , "Red sun could part" , "Tear apart, sever" .)