Told socialist about deceased (7)
I believe the answer is:
related
'told' is the definition.
(as in relating a story)
'socialist about deceased' is the wordplay.
'socialist' becomes 'red' (red can informally mean a socialist).
'about' is an insertion indicator.
'deceased' becomes 'late' (late can mean dead).
'red' enclosing 'late' is 'RELATED'.
(Other definitions for related that I've seen before include "Treadle (anag) - akin" , "spilled the beans" , "Connected by family ties" , "Like family members" , "Reported" .)