Molecular geometry of a compound can be determined by drawing the Lewis structure.
Total number of electrons in ClNO = 7 + 5 +6 = 18 electrons
In the Lewis structure drawn in the image shared, we have three electrons domains around the central atom, two bonding and one lone pair. As there are three electron groups around the central atom, we expect trigonal planar geometry. But due to the presence of lone pair of electrons and repulsions between lone pair and bond pair of electrons, the molecular geometry will be bent.
