Mean spiritualist (6)
I believe the answer is:
medium
This clue is a double definition.
'mean' is the first definition.
(thesaurus)
'spiritualist' is the second definition.
(synonyms)
(Other definitions for medium that I've seen before include "Middle course for participator in seance" , "Average kind of spiritualist" , "Size between large and small" , "Conductor of seances - just average" , "Average; clairvoyant" .)