In this talk, we focus on a class of ideals (called ghostly ideals) in the reduced groupoid C*-algebra C*_r(G) for a locally compact Hausdorff and \’{e}tale groupoid G, motivated by the case of coarse groupoid. We use these ideals to provide a sandwiching result for ideals in C*_r(G), and to study inner and outer supports. We also apply our results to several families of ideals including tracial ideals and regular ideals. Finally, we would like to calculate some concrete examples if time permits. This is based on a joint work with Kang Li.