Mars scheme socialists devised with case for employment (3,6)
I believe the answer is:
red planet
'mars' is the definition.
(synonyms)
'scheme socialists devised with case for employment' is the wordplay.
I cannot really understand how this works, but
'scheme' could be 'plan' (synonyms) and 'plan' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for red planet that I've seen before include "Colourful description of Mars" , "celestial body" , "Informal name for Mars" , "Mars is colourfully known as the . . . . . . . . ." , "object in 21 [SPACE]" .)