Said 'Don't move decoration' (6)
I believe the answer is:
frieze
'decoration' is the definition.
(frieze is a kind of decoration)
'said don't move' is the wordplay.
'said' indicates a 'sounds like' (homophone) clue.
'don't move' becomes 'freeze' ('freeze' is a command to stay still).
'freeze' sounds like 'FRIEZE'.
(Other definitions for frieze that I've seen before include "Ornamental band around a room" , "Heavy fabric" , "this band goes up the wall" , "Horizontal band of decoration on a wall near the ceiling" , "Very greedy eater" .)