Solar system model (6)
I believe the answer is:
orrery
'solar system model' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for orrery that I've seen before include "Planetarium that illustrates the positions and motions of bodies in the solar system" , "Mechanical model of the solar system" , "Err, Roy, on the side of a model of the solar system" , "Clockwork model of the sun and planets" , "Planetary model" .)