Impassive stone idol is moving (6)
I believe the answer is:
stolid
'impassive' is the definition.
(I've seen this before)
'stone idol is moving' is the wordplay.
'stone' becomes 'st' (abbreviation).
'is moving' is an anagram indicator (letters are moved around).
'idol' with letters rearranged gives 'olid'.
'st'+'olid'='STOLID'
(Other definitions for stolid that I've seen before include "Strongly built" , "Not excitable, doesn't show emotion" , "Impassive or apathetic" , "Not excitable or showing emotion" , "Emotionally insensitive" .)