An alternative is to use `Piecewise`  as follows

    Plot[{Sin[x], Piecewise[{{Sin[x], -Pi <= x <= Pi}}, _]}, {x, -2 Pi, 2 Pi}, 
      Filling -> {2 -> {Axis, Yellow}}, PlotStyle -> {Green, Directive[Red, Thick]}] 

which gives

![enter image description here][1]

Or use `Show` to superimpose two variants (the second one with your choice of the variable bounds -- `-Pi` and `2Pi` inn the example below) of the plot:

    Show[Plot[Sin[x], {x, -3 Pi, 3 Pi}], 
         Plot[Sin[x], {x, - Pi, 2 Pi}, 
             Filling -> Axis, FillingStyle -> Yellow]]

![enter image description here][2]

     


  [1]: https://i.sstatic.net/TKRpa.png
  [2]: https://i.sstatic.net/Z0zpo.png