The topic of a child's refusal to obey the parent's instructions came up. I responded:
"Clean your room" is much too vague for the majority of autistics. A better approach is (starting when everyone is calm) to negotiate through a series of steps. Then take one at a time, perhaps one per day. And when I say "negotiate," I do mean negotiate. Many of us have reasons for needing things around us to stay as they are, so it is asking a lot (more than most people realize) to ask us to make changes.
In calm mode, it should be possible to explain why it is necessary to have his room look a certain way. Perhaps it doesn't have to look "pristine." A minimum level of acceptable disorder could be negotiated.
Then discuss how to achieve each step in the change in a way that least disrupts the comfort and reassurance he gets from having his room be the way it is. With some children (perhaps especially younger ones), it may help to "model" the behavior. Say what needs to be done and start doing it, encouraging the child to do it, too.
My mother was still doing things this step-by-step way with me when I
was in my late 20s. Not because I was defiant or sullen.
I was neither. But because she understood that I needed
extra help in taking on motivation from outside, extra
structure in planning/organizing step-by-step ways to
approach tasks (giving me all steps at once was too
overwhelming and drained me of will to attempt even
step one), and help in foreseeing past the disagreeable
focus/energy shift from "being me" to "being me doing
Being encouraged to do one thing, for a clear reason,
for a specific period of time, with a reminder that at
the end of that time I would be able to do something I
wanted to do..... Sounds like a lot of work for her,
doesn't it? But it succeeded, in my case.