The function provided does not work out of the box (and you haven't boxed it in code format anyway) so you have more than the issue of not having the previous dot disappear.
If that were the only issue you could just capture the object when you plot with a handle and then delete only that afterwards before plotting the next, no need to clear with clf and recreate the figure ( ho = plot(...,'bo'); delete(ho) ).
See below.
%% function solsystem(r,T)
r = 10; T = 5; center = [0,0];
bildNr = 0; w = wvar(T);
plot(center(1),center(2),'o','MarkerSize',10,'MarkerEdgeColor','k','MarkerFaceColor','y')
axis([center(1)-r,center(1)+r,center(2)-r,center(2)+r].*1.1), axis equal,
hold on
hp = drawPath(r); %should this just draw just the travelled circular path
% (then put back inside loop and get sector)? if it's the whole thing can stay out like yellow center
for t=linspace(0,10,4) %4 just to show
if t, delete(ho), end
ho = plot(r.*cos(2/pi-w*t),r.*sin(2/pi-w*t),'bo');
bildNr = bildNr +1;
film(bildNr)=getframe; %could preallocate
filmdat(:,:,:,bildNr) = film(bildNr).cdata;
end
figure
montage(filmdat) %immovie/implay or the moving above does not work in online answers
function h = drawPath(r)
beta = linspace(0, 2*pi);
h = plot(r.*cos(beta),r.*sin(beta),'k');
end
function w = wvar(T)
w = 2*pi./T; %vinkelhastighet%
end
% end
