Gdddk

Referring to the question How to make add tick to node in tikz, how do I extend this to a circle shape in TikZ.

A simple approach is to draw lines as ticks by calculating the coordinates. Sample approach below:

documentclass[tikz]standalone
usetikzlibrarycalc

begindocument
begintikzpicture
node[circle,draw,minimum size=10cm] (a) at (0,0) ;
filldraw (a.center) circle [radius=0.1cm];
draw ($(a.center)-(4.5,0)$) -- (a.west);
draw ($(a.east)-(0.5,0)$) -- (a.east);
endtikzpicture
enddocument 

But, this approach is not effective, as the ticks length has to calculated manually.

Is there a better approach to do this (ticks in the circle would be like the lines on an alarm clock, which are inclined execept at 12, 3, 6 and 9 numbers).

Something like that?

documentclass[tikz]standalone
usetikzlibrarycalc

begindocument
begintikzpicture
node[circle,draw,minimum size=10cm] (a) at (0,0) ;
filldraw (a.center) circle [radius=0.1cm];
draw ($(a.center)-(4.5,0)$) -- (a.west);
draw ($(a.east)-(0.5,0)$) -- (a.east);
foreach X in 0,10,...,350
draw (a.X) -- ++ (X:0.2);
endtikzpicture
enddocument 

OK, inside.

documentclass[tikz]standalone

begindocument
begintikzpicture
node[circle,draw,minimum size=10cm] (a) at (0,0) ;
filldraw (a.center) circle [radius=0.1cm];
foreach X in 0,10,...,350
draw (a.X) -- ++ (180+X:0.2);
endtikzpicture
enddocument 

foreach X in 0,10,...,350 loops over X in 0,10,...,350, and then the nodes have anchors given in degrees, so (a.X) is a point at the boundary of a at the angle X. This syntax is mentioned in my previous answer to one of your questions. ++ (X:0.2) adds some shift in polar coordinates, X is the angle and 0.2 the radius. To have the ticks inwards, we need to add 180 degrees to X (one could also use (X:-0.2).)

And just for fun: a watch.

documentclass[tikz]standalone
begindocument
begintikzpicture[font=sffamily]
node[circle,draw,minimum size=10cm] (a) at (0,0) ;
filldraw (a.center) circle [radius=0.1cm];
foreach X in 1,...,12
draw (a.-X*30+90) -- ++ (270-X*30:0.3) node[pos=1.5]X;
endtikzpicture
enddocument 

Use foreach and polar coordinates (with care of course) you can have this

documentclass[tikz]standalone

begindocument
begintikzpicture
node[circle,draw,minimum size=10cm] (a) at (0,0) ;
filldraw (a.center) circle [radius=0.1cm];
foreach i [count=j] in 60,30,...,-270 
 draw (i:5) -- (i:4.5);
 draw (i:4.2) node[font=large] j;

endtikzpicture
enddocument 

In this code, the for loops iterates through the set 60, 30, 0, −30, −60, −90, −120, −150, −180, −210, −240, −270. Each of these numbers is the angle of the "ticks". I use polar coordinate based on these iterators, so the angles of the "ticks" are accurate.

I set a counter for the for loop (j) to add numbers to the picture.

documentclass[tikz]standalone

begindocument
begintikzpicture
node[circle,draw,minimum size=10cm] (a) at (0,0) ;
filldraw (a.center) circle [radius=0.1cm];
foreach i [count=j] in 60,30,...,-270 
 draw (i:5) -- (i:4.5);
 draw (i:4.2) node[font=large] j;

foreach i in 84,78,...,-270 draw (i:5) -- (i:4.8);
endtikzpicture
enddocument 

The second for loop is to draw smaller ticks. 84, 78, etc. are the angles of these ticks.